To clear things up, I’ve put together a basic Twitter guide that explains how to use it, Twitter lingo, privacy options, mobile applications that can be used with the service and problems that it has. Let’s get started.

Twitter limits social-networking updates to 140 characters or less. The service is surprisingly useful, but leaves room for improvement.

What is it? In short, Twitter is a free social-networking tool that keeps people connected with one another and with sources of information. Twitter users submit updates about whatever they’re currently doing, and these updates cannot exceed 140 text-based characters.

Lingo: Twitter is the name of the service. The term twittering describes the activity of updating a Twitter account. A tweet is an individual Twitter update. Twitterers are people who use the service.

Followers, not Friends: Social-networking sites like Facebook and MySpace use the term “friend” to refer to people who are connected with one another, but Twitterers can simply follow one another’s messages by finding a person’s username and selecting a “Follow” option. This alerts the person that you’re following them, and they can reciprocally choose to follow you, or not.

Why use it? While some people primarily use Twitter to post updates about their activities or comments on the news, I use the service more as a follower, allowing me to see quick snippets of news as it occurs. Most tweets are written by real people, while others, such as updates from news organizations that you’ve selected, are automatically generated. Many tweets include the addresses of Web sites with relevant articles that tell readers more on a topic.

Where is it? Twitter works on your Web browser at Twitter.com, where user updates appear in a simple list form as they are submitted. After you’ve signed up and started following other people, those people’s updates, or tweets, will appear when you log onto Twitter.com using a username and password.

Twitter also works on mobile phones, where the 140-character limit allows messages to be sent and received via SMS text messaging. Tweets can also be sent and received via email. Users with smartphones like BlackBerrys or iPhones can use one of the many popular mobile applications for accessing Twitter, which offer much richer options than simple SMS does; I’ll get into these later.

Privacy: Unlike other social-networking sites such as Facebook, Twitter isn’t focused on holding and sharing personal information about its members. Indeed, the service operates with a majority (80%, according to the company) of users opting to keep their updates public, that is, follow-able by anyone, without permission. This openness encourages people to follow one another or to see who others are already following, and then follow the same people.

However, users can opt to protect their updates, meaning they must grant permission for others to follow them. If you’d like to sign up for Twitter, but aren’t comfortable putting your first and/or last name on the site, you don’t have to; instead, just tell others your username.

Twitter Page Personalization: Each user has a Twitter page showing all of his or her updates, or tweets. (Mine is twitter.com/kabster728, and you can follow me.) This page also shows the number of people a user follows, how many people follow her and how many total updates she has posted.

Twitterers can customize their Twitter page by uploading a photo to be used as the background. The icon representing each user can also be personalized, and this is important because it appears beside that person’s tweets on Twitter.com, where followers recognize and appreciate its familiarity. Some people, including me, use pictures of themselves as their icons, while others use random shots.

Apps/Clients: Twitter works on any browser, and will also work on a mobile browser. If you have a mobile device like the BlackBerry or iPhone, you can jazz up the experience by downloading a third-party app like TwitterFon, TwitterBerry, Tweetie or Twitteriffic. Twittervision, another mobile app, plots points on maps to show where tweets originated. Desktop clients also abound, including Twhirl and TweetDeck. Twitterfeed will set your blog to automatically post content to Twitter.

@Replies, Direct Messages: Each tweet that appears in your Twitter feed can be replied to using a shortcut arrow that appears beside the tweet, and these responses to tweets are called @Replies. So if JoeSchmo tweets to say he saw the new James Bond movie and hated it, you can reply to this with a tweet of your own that says, “@JoeSchmo I still adore Daniel Craig.” These @Replies appear for everyone to see, and must start with @ plus the username of whomever you’re responding to.

Direct Messages differ from @Replies because they can be sent only between people who are following one another. These messages aren’t posted publicly. They appear on your Twitter.com page in a right-side section labeled Direct Messages and will also be sent to your mobile device if you have one registered with Twitter.

Favorites: If you read a tweet that you really like, you can save it as a favorite by selecting a small star beside the tweet, thus adding it to a Favorites section on your homepage. Anyone can see anyone else’s Favorites, regardless of whether or not they’re following one another.

Problems: Twitter’s bare-bones approach gets to the point quickly, displaying tweets in a simple, quick-read format. But the site is lacking in many areas. It used to enable searching for people on Twitter, but that capability is currently down. Now, to search for friends on Twitter, you must upload your email contacts from a Web-based mail service. The company says it plans to have people-search working again by the end of the year. Meanwhile, search.twitter.com enables keyword or location searches.

Twitter lacks the ability to sort tweets according to what the user wants. If I just want to see tweets from real people and not those that are automatically generated, I’m out of luck. Same goes if I want to keep certain friends’ tweets in a prominent place on my homepage; Twitter has no way of doing this.

Twitter users aren’t notified when someone responds to their tweet with an @Reply. I recently happened to look at @Replies on my Twitter homepage and found three from people who follow me (I don’t follow them).

If you’re adding a Web address to a tweet and the characters in the URL take up too much space, Twitter will automatically use TinyURL behind the scenes to shrink your long link into a shorter one when you post your tweet. But this works only if you have enough remaining characters in your tweet to fit the long version of your link. A built-in TinyURL converter on the page would help immensely.

Twitter says it’s working to make @Replies more effective. It also says it plans to do more with filtering and sorting, so that the Twitter interface is more useful. In the meantime, Twitter does a good job of giving people simplified news about others and the world around them. If you’re often in a rush, Twitter can be a great resource for fast information.

Edited by Walter S. Mossberg

• Email us at mossbergsolution@wsj.com. Find this and other columns and videos online free at the All Things Digital Web site: http://walt.allthingsd.com

The G1 is built around a model of openness, enabling developers to create applications — software programs, called “apps” for short — that will succeed or fail according to the feedback from the online community. Naturally, these community-contributed programs need a marketplace where G1 users can find them, and the Android Market provides just that.

This week, I installed various applications from the Android Market on a G1 and tested them out. Google (GOOG) says it will launch with around 40 to 50 applications in this virtual store, and these and all other apps will be available free of charge from now until at least the start of next year.

BreadCrumbz makes maps.

I found these apps to be useful, entertaining and mostly straightforward. There were a few that I felt tried to jam too much into one application, such as BreadCrumbz, an app that asks users to add pictures, instructional arrows and labels to maps that they make for friends. Other apps kept it short and sweet, like Wi-Fi Toggle — a one-touch button that turns wireless capability on or off to save battery power.

The G1’s apps are more utilitarian than most apps I’ve tested for Apple’s iPhone — and not quite as visually pleasing. I even compared one G1 program, Plusmo College Football, directly with the same app running on the iPhone, and I missed the artsy touches of the Apple (AAPL) version — like menus that flipped 180 degrees when selected rather than simply opening.

One downside: Only a measly 70 megabytes of internal flash memory are reserved on the G1 for storing these third-party applications. Once you fill that limited internal storage space, you have to delete some of your apps to add more. You can’t currently store apps on the phone’s roomier removable memory card. (A one-gigabyte microSD comes with the G1.) The iPhone doesn’t set such an arbitrary limit on application-storage space. The Android Market, like Apple’s iTunes, keeps a record of each user’s installed apps so they can be easily downloaded again later at no extra charge (if they carried a fee). But, unlike the iPhone, the G1 can’t back up your apps to a PC or Mac.

The G1’s open model means extra setup steps during app installation. For example, if an application will access certain information — such as a user’s Internet connection, location data (as identified by GPS) or other personal information (calendar, contacts, etc.) — warnings appear during installation, and the user must grant permission. In addition, many apps come with license agreements that must be okayed before users can continue. If something goes wrong with an app, people can post complaints on community boards or email developers, whose email addresses appear during installation.

The Android Market home page.

To offer a general idea of what’s available, I’ve highlighted a handful of apps that I like. I broke the applications into three groups: Functional, Fun (if occasionally kitschy) and Frills.

Functional

Wi-Fi Toggle: This does what it says. Once installed, it adds an icon to the G1’s desktop that provides a quick way to turn Wi-Fi on and off without digging into the settings menu.

Locale: Like Wi-Fi Toggle on steroids, this app allows a user to set up a G1 so it dynamically changes its settings in specific conditions. The settings can respond to calls from certain people or changes in the phone’s battery power, calendar, the user’s location or the time. For instance, the Wi-Fi can automatically turn off, ringer volume can go up or down, desktop wallpaper can change or a post can be sent. Just think of all the churchgoers who could ensure their cellphone ringers are turned off on Sunday mornings or when the church’s location is sensed.

Ringdroid: Make ringtones from your own songs by adjusting bars to mark the start and end of each ringtone. Hitting Save automatically keeps the ringtone, labeled with the song’s name by default, for use on the phone.

Video Player: The G1 doesn’t have a built-in way to play videos, and this app does the trick in a clear-cut, reliable way.

Fun

Movie ShowTimes: This lets people use a finger to flick across the G1’s touch screen to page through movie poster images, titles and brief descriptions. Below each movie description, an on-screen button labeled “Showtimes Near You” uses GPS to generate lists of nearby movie times.

Pac-Man: The classic arcade game never gets old. You can move Pac-Man through his maze with one of three methods: tilting the G1 so its accelerometer moves the Pac-Man, swiping with a finger to point Pac-Man in the right direction or using the trackball to move him around the screen. I preferred the trackball.

Cooking Capsules: This program demonstrates food-making without being either too intimidating or too dull and simplified. Though there were only six “capsules” when I tested it, each includes steps for watching (an instructional video), shopping (using an on-screen list of items) and cooking (with numbered instructions on how to cook the food).

Bonsai Blast is a gaming app that’s now available for the G1.

Bonsai Blast: This colorful, Asian-themed game directs people to shoot colorful marbles at other chains of marbles, with a goal of getting three matching marbles lined up beside one another so they’ll disappear.

Krystle II: Turns your G1’s entire screen into a picture of fur that purrs and vibrates as you touch it. There’s no real point, but Krystle II is addictive and strangely comforting during long conference calls.

Frills

Ecorio: This well-intended app aims to track users’ travel carbon footprints in order to make them more responsible for the environment. It asks users to enter things like recent transit routes and carpools and suggests ways to reduce and offset people’s footprints.

Maverick: An IM program that allows people to add scribbles, location data or even photos to active instant-messaging conversations. Maverick signs users into Google Talk and Picasa simultaneously, adding IM images into an auto-generated Picasa album for later viewing.

PicSay: Add word balloons, titles, props and effects to digital photos captured and/or stored on the G1, then send the images via multimedia messaging service or email, or save one as a caller ID.

There are many more G1 apps to try, and developers are expected to keep making them for this new device. As with the iPhone, apps obtained for the G1 from the Android Market enable it to morph into a different device with different tools every day.

– Edited by Walter S. Mossberg

• Email us at mossbergsolution@wsj.com. Find this and other columns and videos online free at the All Things Digital Web site: http://walt.allthingsd.com

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