A tubbed vehicle has had the wheel houses extended towards the inside of the vehicle. This allows the use of wider wheels than stock without widening the body of the car. When this is done, either wheels with a very positive offset (meaning that the hub mounts towards the outside of the wheel) are used, or for more strength, wheels with no offset are used (the hub mounts at the center of the wheel) and the rear axle is shortened so that the wheels do not stick out past the body.
The Body of an automobile is what gives it shape, style, and structure. When we think of a car, the part of the car with which we identify is the body. It holds all the parts together and provides hopefully-aerodynamic surface for minimizing drag, assuming that is what you are aiming for. It provides security and comfort for passengers, again, assuming that is a design goal.
The wheel house is the part of an automobile's auto body|body which covers the inside and top of the rear wheels. It is seen on the inside of passenger cars as a rounded cylinder on each side (one for each wheel), generally immediately behind or to the sides of the back seat in cars which have one.
The radiator support or core support is the frontmost piece of structure in an auto body. Its first name was radiator support, so-called because the radiator is attached to it, but in reality it is the most important part of the front end group. It controls the alignment of the fenders and the hood, and ties all of the parts together - even the headlights are attached to the core support, as are the horns.
The quarter panel is the portion of an automobile's body which corresponds to the fenders in front. It encloses the area around the wheel (in conjunction with the wheel house) and provides the outer skin on the rear of the sides of the car.
A Monocoque (MOW-no-coke) structure is one which uses its outer skin as a structural member to bear shear or load forces due to bending, which is accomplished through the distribution of these forces. They can be divided into three groups - monocoque, semi-monocoque, and reinforced shell. Monocoque comes from a French word meaning "single shell". These designs first came into vogue in aircraft, as a way to save weight by transferring load from a heavy frame to the skin of the craft, which is after all a required component.