Cel Shading

This type of graphic gives the picture a cartoon style due to it already being shaded by being drawn on. This is used in games to purposely give the game shading so that shadows don't need to be rendered. This will mean that the hardware that would be rendering the shadows can be focused elsewhere such as on physics. This type of graphic was made popular in 2000 with the game called Jet set radio for the Sega Dreamcast which demonstrated use of this and therefore got its title of popularizing this type. 
This is an example of cell shading, as can be seen on top of the box and on the arm, there is a shadow on there and very limited elsewhere.