These are the ID's used in game for the objects (bushes, houses, signs, etc.) They also have names, and some are static objects and some can be "placed" on user maps by inserting an object like a barrel in the editor, then editing the mission.sqm and inserting the name of the game object in place of the name of the barrel. Then, the building/house etc. will show up where you put the barrel.
Basically, the ID's can be used to find the names of the game objects
Hoot out!