Cell based animation

Cell animation is a traditional form of animation commonly used in cartoons and animation, its where each frame is hand drawn and its normally 25 fps (frames per second), also these types of animation look flat not 3D. At the beginning of Disney this is what was used in a lot of films like Sleeping Beauty and Beauty and the beast, Hannah Barbara also used this in a lot of her cartoons.
Here are some examples of cell animation.

Tom and Jerry

Scooby Doo

How does cell animation work?
in cell animation you keep the background separate to the characters and any other props, its normally drawn on clean plastic so you can see the previous drawing when drawing the next, most of the time it is 25 fps. It works because each images is only slightly different to last so when it is played faster it looks like a moving image this is also because of persistence of vision.