What You Will Learn
You will learn that a Toggle is accomplished by alternating very similar versions of a prop, every other picture until the illusion of frenetic motion is created. Toggle is the word animators use to describe the switching out of one prop and replacing it with a similar prop to create a loop of flickering animation.
Why Is This Important?
Toggling is used to save time in animation. For instance animation of a waterfall, flames from a jet engine, a fire, or a meteor's tail can be brought to life by simply having two slightly different versions alternate and looped into a repeating sequence.
For example, if a scene has a waterfall in the setting create two different waterfall drawings, and toggle them a few times. Copy and paste the toggled loop, and Voila, a living dynamic waterfall comes to life.