What is a "movie clip"?

A movie clip is best described as a movie within a movie. Each movie clip has an independent timeline in which the animation it contains will play. The movie clip can then be placed on the main timeline and played as part of the "movie".

Movie clips can be placed in a single frame in the main timeline and play for as long as their internal timeline requires. In this way multiple movieclip's can be embedded in a parent movie each on a different layer and each with different properties or behaviors.

Note: each movie clip requires its own layer in a timeline

There are three types of symbols in flash each one with a slightly different behavior, the movieclip, the graphic and the button.

What is The difference between a movie clip and a graphic?
What is a scene?