Twitter is a popular multi-functional (Social networking, Instant messaging and Micro-blogging - All in One) service that helps it's users to connect with their family/friends/colleagues instantly, in real time.
What do you have to do?
~ Create your Twitter account
~ Follow the people you love, meet new friends and get followers of your own...
~ Update in your web box "What are you doing at the moment?" (limited to: 140 characters in length, called "tweets") and let your contacts (followers) know. You may get to know what they're doing in your own tweet board (time line). That is following each other.
To getting to know "Twitter" better, please refer to the official Twitter Support FAQ.
By the way, I'm twittering at http://twitter.com/arkarthick - You can click 'Follow' (under my name) in my profile and get my tweets/or update me with yours.