What, in 140 characters or fewer, is Twitter?

Well, it's a money-losing website made up of very short messages (like this one) where your kids (and C-list celebrities) waste time.

It's also a popular new medium—tens of millions of users and counting—that businesses use to build brands (and sometimes destroy them).

All this you know. Or you should. But Twitter isn't just about buzz: Some companies have figured out how to use it for old-fashioned things.

Like, you know, making money. Here are five strategies. Click on each of the bubbles, below, to learn more about them. And Please Retweet.