Konnichiwa! Welcome to teh FF
I'm Kero, teh one and only Pirate ferret Ninja
A pet is like, well its like having a mate with some of the "benefits" of having a mate without the fur being your mate.
It can be just a very affectionate relationship between Pet and Owner just like the way you treat your pet at home. ^^
Sometimes, in a case I use to have, your FF parent or your mate also can be your Pet or Owner. ^^