Animation: What is it?

Animation:
the technique of photographing successive drawings or positions of puppets or models to create an illusion of movement when the film is shown as a sequence. - Oxford Dictionary 


There are many different types of animation. Today's most common are 2D, 3D and Stop Motion animation.
The last animation I watched was:

The Simpsons - Created by Matt Groening
This is a 2D animation.