Unity is a multi-platform game development IDE that allows users to create 3D games and virtual worlds. It includes a game engine, script editor, 3D terrain editor, animation manager, and GUI system. Games made with Unity can be exported to run as native applications, web players, or on mobile platforms like iOS and Android. Unity uses a Mono compiler and allows scripting using JavaScript, C#, or Boo. Games are created by organizing 3D objects and scenes in a project.