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.
Exactly as you said. In the U.S., undergraduate courses are commonly sorted by level, or the year of study in which they are likely to be taken. See this pattern in the traditional course numbering scheme of 1-99 for remedial courses, 101-199 for first year courses, 201-299 for those of the second year, etc. In this context, "upper division" are those courses for upperclassmen, those past the midpoint of their studies: the ones numbered 301-499.