Cheating in film is the idea of adjusting the location of a person, object, prop or peice of furniture to make the scene look more natural or interesting on screen.
For example, in real life, when hanging out with a mate you may stand 3 feet apart. But depending on the setup and lenses being used, this may look weird on screen. This is where you would cheat your position by being closer or further away from the other actor.
Similarly, you may cheat by moving the position of the scene to account for the sun. Lighting is one of the most important parts of film, and the sun is the biggest source of light. Therefore, the director may flip the scene around to make the source of light come from another angle.