Follow-Through - When movement is continued due to momentum. For example in Sonic, when running right you pick up speed but if you were then to let go of the controls, Sonic would keep moving, progressivly slowing himself to a halt.
Exaggeration - This is when a body part is out of proportion, to enhance or "exagerate" a feature. For example, if a character was supposed to be overweight, he would most likely be made much bigger than usual overweight people, so that it becomes a noticable trait for this character.
Balance - This makes sure that the character balances realisticly on different surfaces. For example in Tomb Raider: Underworld, when Lara Croft crosses thin beams, the balance animation bends her spine to the left or right as she tilts.
Squash and Stretch - is when a part of the character is stretched or squashed to give an effect. It is seen commonly in games with a cartoony art style, like in Bugs Bunny: Lost in Time when an enemy hits Bugs over the head with a hammer, he gets squashed down to show he was hit.
Secondary Action - This is when a character does something, which in turn causes something else to happen. For example dropping something into a pool of water would cause a splash.
Anticipation - Anticipation is build up to something happening. For example, if a window breaks and you're all on your own in a big scary zombie-infested mansion, and you didn't break it, you can put good money on not being alone anymore. Another example would be bubbles reaching the surface of a pool of water before something emerged from it.
This is a link for a video detailing how balance is used in animation.
https://www.youtube.com/watch?v=_IT0EEVdkOE
