A rigged model is a skin stretched over bones. A movement turns the bones and the skin follows, which is why one fox can survey, walk and run without three copies of it existing. Press 1, 2 or 3.
It does not cut between them. fade says how long to take turning the bones from where one movement has them to where the next does, and the mixing happens at the joints, not between the two shapes: that is what makes a change of gait look like an animal rather than a dissolve.