Each one has its own special place in the world.
Raster editors are programs that edit graphics using a bitmap of colors, or pixels.
These are probably the most common. These include programs such as Paint Shop Pro and Photoshop. Raster images are generally large because every pixel has to be saved, yet they're more detailed because of the fact that every pixel is saved. Vector Graphics are a little different from raster. The file sizes are very small because instead of every pixel being saved, the methods to render the images are.