The Warthog is a four-wheel drive combat vehicle. It holds at least one driver and two passengers, one who mans a rear-mounted gun, which can be a rocket launcher, a chain gun, or a Gauss gun.
In the first game, the Warthog was indestructible, as were all human vehicles, both in the single-player campaign and in multiplayer. In Halo 2, it can be destroyed in stages, killing or wounding the occupants and other nearby units.
Other configurations (not shown) forego the rear-mounted gun and instead carry extra passengers.