What does "upper division" mean in the context of undergraduate classes?

I'm in the process of researching graduate programs, and one of the ones I'm interested in prefers their applicants to have a B average in "upper division" classes. I just want to clarify what this means. I'm in a 4-year undergraduate math program, so would "upper division" be 3rd and 4th year courses, or would 2nd year courses be dragged into the mix?

Edit: I am talking about US grad schools, but I go to a university in Canada. Right now, I have a GPA of about 3.3, which I hope to surpass in 3rd and 4th year to look better on my grad school app.