Animation is "the illusion of motion." In description, animation is a set of techniques for the creation of moving pictures, in which each frame is created individually.

There are several types of animation. Traditionally, cel animation refers to "cartoons." It is the simplest animation. The second type would be puppet animation. It is also known as "time-lapse photography" due to its application of time lapse to deceive the perception of human eyes. Clay animation or model animation is also known as "stop-motion photography." Recently, a Nissan's commmercial which features its famous DX-3000 and "Barbie Doll" is categorized into this type. The fourth type of animation is pixillation. The different combinations of images are used to create the impression.

The last and latest type of animation is computer animation. Animators seldom use real pictures or models. The computer drafts and animates all images.

The example I provide above is a cycle animation. The cycle animation is one of animation methods. It can be used from cel animation to computer animation.

The two methods of cel animation are straight-ahead and keyframing. The development of computer animation is stemed from the keyframing cel animation. Therefore, computer animations are all keyframing.

3D animation is always done on a computer. It creates photorealistic images by calculation the appearance of three-dimensional objects with particular surface properties, in particular lighting situations, in 3D space over time.

The steps of 3D animation are:
1. Modeling. 2. Materialing / Shading. 3. Keyframing. 4. Rendering.

Source from: Jose A. Acosta, Former Director of Computer Animation, The Art Institute of Atlanta.

Reference:

rob bredow

Animation

Motion Picture

Computer Animation

Computer Graphics