A real life garment used by the military, a poncho like material is attached with fresh leafs and woodland materials so the user can blend in with the given enviroment. A suit donned by Snipers, typically SAS and such.
The Ghillie has also featured in FPS video games, COD4, CODWAW, this gives the user(a sniper can only use them) a tactical advantage when it comes to grassy areas, but the developers pulled them off poorly and they rarely work.

the bush that just shot you

a camoflage suit, popular with snipers in any terrain, to pick of enemy without being spotted, appeared in the game ghost recon (though to not much effect), its especially usfull to pick of the nasty Arabs and Iraqi's, It was also used by gamekeepers to keep a look out for poachers

Ghillie suit is a gear that allows you to blend with the environment. It is commonly used for hunting, paintball, bird watching and wildlife photography.
Ghillie suit is your best chance of getting invisible in any terrain. The trick would be matching your ghillie suit with the terrain you will be in.