vector art isn't cel shading, vector is a mathematical way of making images and text in 2d, cell shading is a 3d app. If you want to do vector work try programs like macromedia freehand and adobe illustrator. photoshop has some basic vector abilities but not near as much or as nice as the first two. Here is an example of one of my works with vector https://www.wincustomize.com/skins.asp?library=8&SkinID=10637 it was all compiled in photoshop, but the vegeta character and the DBZ logo were done in freehand as vector work.
The reason vector is so nice is because it works not with pixels but mathmatical equations, which means it is infinetly scaleable up or down without loss of information, and files are small in comparison. hope that helps explain it better for you