Key Frame

Definition: An animation key frame is a single still image in an animated sequence that occurs at an important point in that sequence; key frames are defined throughout an animated sequence, in order to define pivotal points of motion before the frames in between are drawn or otherwise created to "tween" the motion between the two key frames. One example of key frames could be an animation of a swinging baseball bat; the bat at rest would be one key frame, and the bat at the end of of its swing would be another. All other frames would be "tweened" frames.