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.
PhBR says
Garry's Mod allows you to create anything using valvE's objects and characters , but , is it easy? When you play GMod at the first time it's hard to create anything.
The NPC'S AI aren't so good but it's aways funny to kill combines or zombies. You can do something like a GAME , survival missions , deathmaches , explosions , everything you can imagine you do.