What is "Crontab" and how do I use it?
 

All I know is that it seems to be some sort of timed repeating program on the server.

How do I use it though?

If you are not on dedicated or hosting in your own computer, you dont need to worry about how you use them.

In most hosting companies you just ask them to configure it for you and they dont let you configure it yourself. You just give details (which script will run when) and they do all the stuff.

And some of them dont even allow users use this feature. So you'd better ask them.

My shared host let's me use them. I use them to do database backups.