Gmod is a mod for half life 2/Source engine, it gives the player a load of tools to mess about with, far from a game creating software.
Quote from the
website.
Quote: " What is it?
Garry's Mod is a sandbox mod for the Source Engine. Unlike normal games there aren't any predefined aims or goals. Players are given tools and are left to entertain themselves.
The player is in a world where objects can be created and destroyed on demand. Where people can be created and destroyed with the click of a mouse. A world made for him. A world he made. "