What is Cracking?

I've seen threads about different types of cracking on different accounts, and I was wondering what that is lol :

Cracking is when you (typically) brute force a set of emails with a list of passwords and hope that one of them is their password. Running a program that does this automatically is usually a "cracking tool" that you see a lot of on these forums. Then what people do is take these account lists and sell them to people who want to use them.