Could someone explain Twitter?

[Steven T]

PLEASE READ BEFORE ANSWERING

I'm not 'behind the times' or 'technologically retarded' I know what Twitter is and how to use it and blah blah blah, what I really need someone to explain to me are the following things:

RT
@
#

And anything else you think might be pertinent, such as how to network, trending topics (and why I should care), and whatever else the Tweeters of the world can share with me.

Once again DO NOT tell me that Twitter is a social networking site where you post short quips in 140 characters or less or a pox upon your house.
Come on people, if I ask you to read could you at least try? I just need something in the form of "# stands for _____, you use it this way, these are the reasons you do it, it's cool for this reason, etc..."