Some traditional methods used in animation are
key frames, cel animation and rotascoping. What you use these for
is to make the animation better, quicker and more complicated. Key Frames
are the main points of the animation where most of the action takes place.
Cel Animation helps when you are drawing the picture because when you use
it you dont have to use the entire frames. Rotascoping is when you copy
images from moving videos into an animation. For example if
you animated a bunny hopping. Each tiny movement would be very hard
to visualize in your head.With the help of rotascoping, you can animate
some complex scenes that would be very hard to visualize without it.