Ok, so there's two things in my discrete math class that we've just started learning that I'm just not getting.

1) What is a codomain?

2) What does it mean when a function is "onto"?

I need more than definitions... I'm not getting it when I have to do actual problems.

For Discrete math question:

Co-domain rather loosely is another word for where the equation maps a set to. X is a set, Y is a set. A function maps X into Y. X is the domain, Y is the co-domain.

The standard intuition is that you have a function machine, you dump in x's (from the domain) and the function machine churns out y's (from the co-domain.)

Onto,loosely means that every possible y is landed on by an x sent throught the function F.

Onto
Co-domain

Answer: courtesy of another AnswerPool member, "notinmyname"

Hope this helps!
~Lydia