Stop motion anmation is a way of creating films. The character (a toy or clay model) has it's picture taken. It is then moved a tiny bit and has another picture taken. After about 15 frames (pictures) you have 1 seconds worth of film!
Some examples can be found @ (don't wan't to advertise, just giving you some help):
Wallace and Gromit
Pingu (I think is a stop motion)