What does it mean to "watch a topic?"

I'm not sure if the explanation for this is posted somewhere on the site, but I'm curious as to what it means to "watch a topic." I was hoping you guys could help me out with this.

Oh shit! I love that there are rules and guidelines on the right side of the screen when making a post now! That's awesome!

Well, isn't it like a "follow" button? I think it is. When the topic gets a reply, then you get a notification. Erm, I might be wrong.

Edit:

It looks like it also locks it under the thread that are sticky.

No, that can't be right. I'm "watching" this topic now, but I didn't get any sort of notification when you posted in the thread. Also, I don't know what a "follow" button is either. Isn't that some sort of Twitter concept?

The sticky thing is pretty cool though.

It looks like it is still buggy. I have tagged like 3 topics and if I refresh the page the topics just fall under the last replied topic. Also, I don't think follow is a twitter concept it's just a system keeping track about a certain topic you tagged and stuff.