Twitter

Twitter is a website, owned and operated by Twitter Inc., which offers a social networking and microblogging service, enabling its users to send and read messages called tweets. Tweets are text-based posts of up to 140 characters displayed on the user's profile page.
The website is based in San Francisco. Twitter also has servers and offices in San Antonio and Boston. Twitter, Inc. was originally incorporated in California, but as of 2011 is incorporated in Delaware.
Twitter was produced in March 2006 by Jack Dorsey and launched in July. Since then Twitter has gained popularity worldwide and has had 200 million users, generating 350 million tweets a day and handling over 1.6 billion search queries per day.It is sometimes described as the "SMS of the Internet".

Features

Twitter has been compared to a web-based Internet Relay Chat (IRC) client. Tweets are publicly visible by default; however, senders can restrict message delivery to just their followers. Users can tweet via the Twitter website, compatible external applications (such as for smartphones), or by Short Message Service (SMS) available in certain countries.While the service is free, accessing it through SMS ma y incur phone service provider fees.
Users may subscribe to other users' tweets – this is known as following and subscribers are known as followers or tweeps (Twitter + peeps).
Twitter allows users the ability to update their profile by using their mobile phone either by text messaging or by apps released for certain smartphones / tablets.

Messages

Users can group posts together by topic or type by use of hashtags – words or phrases prefixed with a "#" sign. Similarly, the "@" sign followed by a username is used for mentioning or replying to other users. To repost a message from another Twitter user, and share it with one's own followers, the retweet function is symbolized by "RT" in the message.
In late 2009, the "Twitter Lists" feature was added, making it possible for users to follow (as well as mention and reply to) lists of authors instead of individual authors.

Twitter for Android App Gets Major Boost

Twitter recently released an updated version of its app for Android this July. The newest addition to its features are push notifications and multiple accounts support.
The inclusion of push notifications in this update might be an improvement or a mere redundancy for Android users. It can be a good sign as it levels the field for both Android and iPhone, with the latter already enjoying the feature since last fall. It might also be a little redundant for some, as Android also allows users to be updated of their Twitter whereabouts through the notification bar. This feature however will be appreciated by those who need to check their mentions every now and then.

As for the support for multiple accounts, this update has been long-awaited. Now, Android mobile users can switch and tweet from one account to another, without having to log in and sign out all the time. This feature is much help to businesses, with earlier experience on multiple account support only provided by third-party clients. However, this feature remains to be isolated to Twitter for mobile. Like the push notifications, iPhone users were the firsts to enjoy this feature, back when Twitter for mobile was still a third-party app called Tweetie.
Other updates to version 2.1.1 include an updated home screen widget and bug fixes for HTC users being asked to sign in repeatedly and for cleared notifications once user logs out.