Stop Motion, is actually a way of making objects appear to move by animating inanimate objects. The art of stop motion is really quite simple, much like the technique used by artists to create cartoon animation, but instead of drawings 3D objects are used.
Any tangible object may be used to create a stop motion video, however the most interesting objects are pose-able, such as articulated puppets etc. Some stop motion puppets are actually made of clay, or plasticine, which is a bendable rubber like material which in most cases if formed around some sort of internal skeleton, also known as an armature. More complex puppets feature life like eyes, skin and and overall realistic appearance.
An armature can be created with something as simple as bendable copper or aluminum wire, although the best type of armature (also known as a maquette) is built from of a series of ball jointed objects linked together to form a basic character shape, whether it be a man or monster, the construction is the same. Today basic kits are available for around $100 and include enough parts to make a simple but practical maquette.
The basic technique of stop motion is to position your puppets in a starting position, then take a single frame image (photograph) of your setup, then change the position of the object or objects limb ever so slightly from its starting position. Do this repeatedly until your puppet has completed the desired range of motion, then when played back at a normal speed of 24-30 frames per second, the object(s) appear to be moving on their own.
Several factors will affect the quality of stop motion videos, such as lighting, minuteness of movement, and stability of the camera itself. Professional stop motion animators use magnetic bases to record the position of each limb prior to each adjustment. This helps create more subtle, less abrupt movement.
Stop motion can be created using any camera capable of exposing single frames. Web cams provide an inexpensive alternative and produce acceptable results with the help of stop motion software such as iKITMovie or Stop motion Pro version 6.
The rest is up to your imagination!
Here is another nice video that talks a little about stop motion.