Just what is "Twitter"?

Topic: Twitter|Level: Beginner|Type: Informational

Twitter is basically a super-simple social-networking or "micro-blogging" service. It's a way to keep up on your friends or celebrities or whatever topics people are talking about and a way to let others know what's going on with you.

Tweeting
"Tweets" are short (140 character max) updates and messages people post. One of the main things that has made Twitter so huge is because it's so easy to post tweets.
via Websites: You can of course post your tweets and read what everybody you're following is up to from the main website (twitter.com) or from the mobile site (m.twitter.com). Of course all your account setup is done from the website as well. But more commonly you'll probably end up interacting with the Twitter service from some of the other options...
via SMS: Another very common way to tweet is through a cell phone SMS text messaging. Once you create your Twitter account, you can link your cell phone number and once set up all you have to do is send an SMS text message to 40404 (or other numbers available for outside the U.S.) and your text message is posted as a tweet. All the services from Twitter are free, the only monetary costs are if your cell service provider charges you for text messages.
via APIs: Twitter also makes their APIs publicly available. So any software developer can pretty easily make something that will post tweets and many can even show you tweets from people you're following. There are applications that integrate in to your web browser, ones that are stand-alone applications to run on your computer, ones that run on cell phones (on nearly any carrier/platform), nearly anywhere software applications can be written, there's an application available that implements the Twitter API.
"TwitterBar" is one I like that is a Firefox add-on that you can type a tweet message directly in the address bar on any page and a special image button shows up at the far right end of the address bar that when clicked posts what you have typed as a tweet.

Following/Followers
Once you have your Twitter account you can "Follow" your friends or celebrities (and anybody else can then Follow you) and then from your homepage (or whatever application you chose to use) you can see all the tweets from the people you're following sequentially.
To Follow somebody, you of course first need to Find them. The "Find People" link from the Twitter home page allows you to search for people by their name, by their email address, or you can even provide your email account and password and the Twitter service will check all the email addresses in your address book and find any of them that are set up as users. (Some people may not want to use this as it does give your email address and password to a company other than your email service provider, but the Twitter service does not store your password at all and they are a reputable company, so it is safe in my opinion.)
You can also find people easily if you're given their Twitter username. For example mine is "nickolashook", so you can get directly to my Twitter page by going to twitter.com/nickolashook.
Once you find somebody all you have to do is click the "Follow" link and that's it.
You can even start Following somebody from your cell phone if you have it linked to your Twitter account. You simply send a text of "FOLLOW username" to Twitter and that's it.

Getting Updates
You may end up having lots of people you're following on Twitter, then want to get the tweets from a subset of them sent to your cell. Once you have your cell linked to Twitter, all you have to do is go to your "People I'm Following" page (twitter.com/following) and click the little cell phone button beside those people and that's it. You can also from your account settings page set a "Sleep" time, in which updates will not be sent to your cell.
Or you can start getting updates sent to your cell by texting "ON username". You can also start Following somebody and get updates from them in the same text with "FOLLOW username, ON username"

@ Replies
You can post tweets that are directed at a specific person, but are still in the public timeline. A message such as "I'm Dumbfounded @nickolashook" would show up publicly, but I'd get a special notification through the website that a message had been directed at me. Also, others reading that message would be able to click my username to be taken to my page.

Directing Messaging
You can also send Direct Messages (or "DM") to other users. A Direct Message is one that's directed at a specific person and only can be viewed by them. To send a Direct Message you post a tweet in the form of "D username Your message". For example "D nickolashook Hey, what's up" would send the message "Hey, what's up" directly to me and only would be viewable by me. Direct Messages sent to users with mobile updates enabled even get the message sent as an SMS text message to them.

Tweeting Pics?
Twitter itself does not provide a direct option to post photos. However, most users use a service such as twitpic.com to post photos. You log in there with your Twitter username & password, and you're given a special email address to send photos to. Photos then sent to that address are uploaded to their servers and a tweet is posted with a link to that photo.

Topics & Trends
One of the other things Twitter is renowned for is you can search the social web for news on various topics as it happens or just see what people are talking about at that moment. The Search finds tweets on whatever you want to find.
Users also tend to use "hashtagging" in their tweets when posting messages of a particular topic. A hashtag is a pound or hash sign followed by some text that users can then Search for to find tweets for that topic. For example, recently everyone who was talking about the Obama inauguration were using #inaug09. This way you could search for this to follow the conversation.