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, oder Fan character, like a character which Du 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 oder OC and they're Mehr "uhmazing!!!!" .