Squash and Stretch-
Squash and stretch is to give an object or character the feeling of flexibility and weight - This can easily be demonstrated on something like a bouncing ball. Squash and Stretch exaggerates the balls normal movements to make it look more believable. The ball wouldn't change its mass, just its shape depending on the movement its doing.
The idea of anticipation is to prepare the audience for a major action that the character or object is about to perform.
The purpose of staging is to clearly make the characters/objects facial expressions and/or actions understandable for the audience to follow.
Straight ahead and Pose to Pose Animation-
Straight ahead animation is when you start from your first slide and work your way through to the end in chronological order. This can be a good technique, however for a more planned animation sequence or more challenging animation Pose to Pose animation would be required. This is when key frames are chosen through-out an animation sequence, drawn first and then the other slides come in later.
Follow through and overlapping action-
This is when an object or character for example would stop but things like their hair and clothing would carry on, this gives a sense on movement and flow when animating a character, it also gives the character a realistic feel to them because if a girl was wearing a long silk skirt whilst spinning around, when she stops the dress would carry on going, this is the principal that also needs to be used for animation.
Slow out and in-
Every character needs a speed in which they are travelling, when an object/character is moving it is better to add more frames at the beginning and the end of a movement, this gives it a more realistic approach and exaggerates the more important parts of the movement.
All living creatures follow curves/ arc shaped trajectories when moving. This can be seen in a pendulum swinging when it swings back and fourth it creates an arc.
This is when an animator adds in extra parts to the sequence to make the character or animation itself more interesting. This could be an angry person walking along the road, they would be lent over and doing short aggressive steps with their hands by their sides, fists clenched. To add a secondary animation to this an animator would have the character move their arms or fists, mutter angrily to themselves, or even kick something like a can on the floor. This adds more interest but doesn't distract too much from what the character is currently doing.
Timing is how long it takes for an object/character takes to do a movement; such as rolling a ball from one side of the screen to the other, the mass, weight, floor surface etc should be considered when the object moves during the sequence.
This is essential for animation, exaggerating movements and actions is very important when animating as in real life the sequence would be less interesting and make the animation boring, also with animation not adding exaggeration can make it look really fake and unrealistic.
An animator must have the key concepts and have a good understanding of 3 dimensional objects and shapes. Weight, Light, Shadow, Solidity and Volume have to be well known and second nature when an animator is making an animation otherwise it can be disjointed and not make the objects/characters moving look realistic.
Appeal is making a character link to the audience, no matter if villain or hero, the character should be clearly drawn and have an easy to read character that the audience can associate with. This can be done for objects as well where it could have appealing movements based on its character or interact with the audience.