In a conventional modern car, the bodyshell is the combined body and chassis unit, in which the body panels contribute to the strength and stiffness of the whole structure.
Reinforcing members are built into the large steel floorpan pressing to resist the biggest forces. Bulkheads, bodyside pressings, inner wings and other panels are spot-welded to the floorpan to form the bodyshell structure.
This method of construction is also known as unitary, uni-body or monocoque.
Note that a car with a separate chassis has a body not a bodyshell, because the body does not act as a stressed, structural part of the vehicle.
