A primitive is an object that is parametrically defined by a set of parameters. A sphere, for example, can be described by its radius and height and width segments. A mesh object is defined by giving the exact location, or offset, of its vertices in relation to the object’s transform axis. Most engines will have at least a few primitive objects for simple-use cases. They are most useful for experimentation and, occasionally, projectiles. While a primitive object is smaller on disk, once in the game, it will go into memory, just as any mesh-type object.