This is a stupid beginner question but I really need some help.

I have two list of names. One consist of recently added user names the
other is older and not up-to-date.
I want to compare the two list and only extract those that are unique to the
two. This would give me the new
people only. I CAN NOT FIND OUT HOW TO DO THIS!!!! I know this is basic
stuff -
I would appreciate any help you can provide.

Thanks
Curtis