Anticipation prepares the audience for the main action of a character or element in a scene, including things such as jumping, a change in facial expression.
When a dancer goes to jump into the air, a backward action to prepare for the jump occurs. This is the anticipation for the jump, demonstrating the energy needed for the jump to occur.
Anticipation can also be used to to emphasis things such as gags and the comic elements to a scene.
A very computerised voice showing the principle of animation. Video courtesy of Gilles Charbonneau.
The pause at 0.51 seconds on the camels expression as he moves from the bored expression to one of happiness adds to the mood of the piece.