I think I have yet to meet a Linux distro that didn’t include cron, in some fashion or another, by default.
I suppose in that sense it doesn’t bear my explanation. I’ve used it only rarely by design; other times, it was just running by default.
crontab is an underling to the daemon. If you want to get started with cron, the comments in the basic
crontab -e display will give you hints.
If you need more of a jump start, you could look over this quick how-to that some geek wrote, years ago.
More help than that, and I would advise you to take a peek at the finest collection of computer know-how in the history of Linuxdom … the Arch wiki. 😉