How is Twitter used and how does it work?

[MCorporalAdams]

I signed up for twitter about 3 years ago, and now someone has told me to start using it.

I have no idea how it works, and why people use it... but if someone could explain that'd be great.

I know it's updating your profile for everyone to look at, but as a social networking site, I've seen that certain people communicate using the "@" sign.

Can someone give me a brief summary of how Twitter is used?

Thanks
By the way, I realize this is in "Facebook" but there's no "Twitter".