Chance Agrella at photoshopsupport.com does a great job explaining the difference between vector and bitmap graphics. This is something any graphic designer in training needs to know backwards and forwards. Not just the differences, but the benefits and disadvantage of each.

Vectors And Bitmaps – Guide To Photoshop Basics

As people begin working with computer graphics, one of the subjects of greatest confusion is the difference between bitmap graphics and vector graphics. This article will attempt to define both, then explain them as they relate to each other. I’ve tried to start as simply as I can while offering some tips for intermediate users about working with each.