Dispersion is just the process of refraction when it happens at an angle to a surface (causing light beam bending, so that the white light is separated by frequency because of the frequency dependend electrical properties of the material acting on the electric field of the light). Refraction straight on doesn't bend anything, just changes the speed of the light.

I'd just call it 'refraction' myself. It's confusing to have two terms for the same phenomena. But 'dispersion' seems to be the accept term, according to Wikipedia, and the Wikipedia definition doesn't even mention refraction - weird.

One of my pet peeves is when explanations are self referential, just using scientific names as if the name itself were an explantion of anything - yet never mentioning how any of it WORKS. This definition is a good example of that.
http://en.wikipedia.org/wiki/Dispersion_%28optics%29