Objects perform the action in an animation like cast members in a movie. For example, in an animation of three geese flying across the sky, each goose is a cast member.
You can draw or import objects that you want to use. In many cases, you will save time by converting objects to symbols.
Tweening between instances and distributing them to frames can be much faster than placing individual objects on each frame.
For more information on symbols and tweening, see Tweening instances.