Okay...so, as the program starts up it goes through a series of program statements. One of which, reads:
initializing engines
Engine (slang from the English "engine" - motor, engine) - a dedicated part of the program code for the implementation of a specific applied task - a program, a part of a program, a program complex or a library, depending on the task and implementation. (from Wiki)
In 3D games "engine" is a frequently repeated section of the program code that is responsible for the display of the formed frame on the screen