Twitter is a very well known social networking site and biggest plus point is most of the celebrities either from any hollywood or bollywood stay active on twitter.
I have been using twitter from last 2 year and here is my personal experience
It is different from facebook, you follow people you get followed.
You can tweet your social activity to your followers in 140 characters
When you will make a good friend circle on twitter then youll find it entertaining
You can chat in direct message.
Good site according to me, 4/5.