I'm following 139people - mainly celebs. But that's because I run a celebrity gossip website.
If you have Facebook then basically, Twitter is the updates section of Facebook, where people write their status and you can reply to it etc. To reply to a "tweet" all you have to do is hover the cursor over the right hand side of the status and clicking the arrow. In your status box it will come up with "@(username)" then just type your reply after that.
If you want to send a direct message to someone just type in "@(username)" for instance, to send a comment to Davina you write @ThisIsDavina [your message here].
You "Follow" people to see their updates but they don't see yours, only if they follow you.
Follow me at
www.twitter.com/ChrisCoutureUK