FAQ: Vector Graphics
Most of the graphics you see on the Web today are bitmaps; that is, they are made up of a set of pixels, each one a different color, combining into the patterns that make up the image. When you create a bitmap, you use a graphics application to essentially decide which pixels will be which color and what the dimensions of the image should be. Simple enough. But what happens if you want to change the size of the image? Well, you either start over and make a new graphic, or you stretch it - with generally unpleasant results.

Enter the vectors. Rather than assigning colors to pixels, a vector graphic application lets you draw with lines and shapes. Essentially, a vector graphic is a series of commands that might dictate a line's direction, thickness, and color, which gets rendered on the screen later. The benefits are obvious: The files are very small (each pixel need not be accounted for), they can be resized to any proportion, and they are eminently flexible because they can simply be re-rendered at any point.