Twitter what's its purpose?

Okay, I'm not sure if I'm the only one but what is the deal with twitter? I mean really what is the purpose? I have been sitting here for about 30 min trying to figure out what to do with it. I have followers and am trying to follow others. I also have options to do nudge some and not others, I added a pic but that's about it. I also read Dr. Z's blog and followed the steps to add it to my computers so okay what now?

I nudge Dr. Z just because, I just wanted to see what it meant. Is twitter like instant messaging? Is that why I added it to my desktop? I need some clarification please?