A gamer is a person who plays interactive games, especially video games, tabletop role-playing games, and skill-based card games, and who plays for usually long periods of time. Some gamers are competitive, meaning that they compete in some games for money. There are many different gamer communities around the world.

The core functionality typically provided by a game engine may include a rendering engine ("renderer") for 2D or 3D graphics, a physics engine or collision detection (and collision response), sound, scripting, animation, artificial intelligence, networking, streaming, memory management, threading, localization support,..