An engine may refer to any of the following:
1. The part of an application that controls the manipulation of data. Don't confuse the engine with the interface or with things such as device drivers, which help the software work with components in the computer.
2. When referring to a processor, an engine refer to a special processor inside a computer that speeds up graphics and printing.
3. In gaming, the engine refers to the main portion of the code that controls how a game works. Many larger companies will license out their gaming engines to other companies to offset the costs involved in game development. For example, Gears of War is a game that uses the Epic Games Unreal engine.