Ambigear Cube is a 4x4x4 Rubik's Cube with a gearing mechanism inside. It's name is from "ambiguous gearing". In a regular gearing mechanism, all parts have direct interact with each other and if you block one part then the other parts are blocked as well. Not for this mechanism. If you lock the top two layers to each other then the top two still mesh. Same for the bottom two layers and middle two layers. This makes the puzzle confusing to solve.
This puzzle uses the same gearing mechanism as the Geared 1x1x4, which has two linked planetary gear systems.