What is "diversity"?

I attend a VERY small liberal arts college, and the administration is paying a design firm to re-brand our course of study. One of the main goals of this re-branding campaign is to attract more “diverse” students. What they seem to mean by this is more women and people with differently pigmented skin (my school happens to be mostly Caucasian males, although not overwhelmingly so; we have about a 5:3 male to female ratio).

Especially in undergraduate education, there seems to be a huge push to get a student body with lots of people who look different from one another. But isn’t the important thing that people think differently, that they offer an environment rich in unique experiences and points of view?

What is diversity, and why is it important; are institutions just trying to cover their asses by hiring/accepting lots of people that are superficially diverse? Should anyone be actively trying to attract people who may not be interested in the specific goals of their institution by lying to them about those goals?