What are AU and OC couples?

AU is alternative universe, as if the characters are in a different universe (like Gakuen Hetalia).
OC is original character, or fan character, like a character which you made for a series that isn't cannon.

AU = link
Can't find the other one :/

I don't read fanfiction, so I wouldn't know.

PS.
Go read real books. They have no AU or OC and they're more "uhmazing!!!!" .