How the heck does Twitter work?

[Thriller]

Haha. I am VERY new to twitter. And I'm wondering...what do things like '#' at the beginning of a word mean? And when the hell are you supposed to use that? And also, why are there '@' signs at the beginning of people's usernames. And how do you communicate with other people such as celebrities...is it like Facebook, where you write on their 'wall'? lol. Help would be greatly appreciated. =)

[Jojo]

in facebool you can write status and all but in twitter all you can do is give off small messages about a certain topic which interests ppl...thatz it.