What are timeouts in chess?

The help section of this site is quite handy ;)
What are timeouts and why can't I join tournaments because of this?
As Sunshiny suggests.. ye can take vacation time.. to prevent timeouts..
I’m going to be out of town for a while, but I don’t want to lose my games!
its not a timeout in the sense of American football fer example.
Here's the link to the vacation FAQ:
http://support.chess.com/index.php?_m=knowledgebase&_a=viewarticle&kbarticleid=31&nav=0,6Looks like Pistoleer posted the same link first.

A Timeout means that you lost by running out of time to make your move. Vacation prevents this from happening - it's like freezing the clock.
If you don't have any vacation time left, but you're not going to be able to login for a while, resign all your games. Your rating will recover a lot faster than your timeout percentage.
What are timeouts in chess? I mean theres no button. Whats the point of it and how does it know if your using a timeout?