I dont understand how it works to be honest
You use text messages on your phone? It’s like that.
Sending messages to @someone will send to them but is publicly readable. You can send private ‘direct messages’ with D someone instead. Otherwise, messages just go out there where anyone following you will see them, or anyone looking at your Twitter page.
If you like what someone writes, follow them. If you don’t, don’t.
When you get to following a few (and you’ll be surprised how quickly you go from “how do I find people to follow?” to “jesus christ, how do I keep up with all this?”), consider using a dedicated Twitter client such as Tweetdeck. Tweetdeck lets you list your followees in columns, so you can put (for example) STW people together. Personally I just have two inaccurately named columns, “friends” for people I actually know and “celebs” for everyone else.
I’m @UKCougar, should anyone want to read my drivel.