Compound transitions are best thought of as a blend between Simple/Complex and Duplex. Connecting a one-foot landing to a two-foot takeoff (or vice versa) will produce a Compound transition; below are the two natural and most common forms.
Common Compound Transitions
A Pop transition created by connecting an ordered landing (any order) into a takeoff from both feet. This transition does not change its name when an adjustment is made to stance or position to create an artificial form; both vert and invert tricks stay the same regardless.
Reverse Pop(opposite Compound)
As its name implies, the Reverse Pop transition connects a landing on both feet to a takeoff from either (any takeoff other than Pop.) Adjusting this transition to create an artificial one could be labeled a "Bound," and it would still be classified as a Compound transition.