A vehicle structure where the body shell carries the load. The standard for most modern passenger cars. Lighter than body-on-frame but harder to repair.
Monocoque (from French for "single shell") is a vehicle structure where the body shell itself is the structural element carrying loads. Unlike body-on-frame designs (where the body sits on a separate frame), a monocoque integrates the structure into the body panels. The approach is also called unibody construction, especially in North American usage.
Most modern passenger cars use monocoque construction. The advantages are lower weight (no separate frame to add mass), better packaging efficiency, improved crash performance (crumple zones can be engineered into the structure), and lower manufacturing cost at scale. The disadvantages are difficulty of repair after major damage (the structural panels are integrated and harder to replace), reduced ground clearance flexibility, and limited towing capacity compared to body-on-frame designs.
Trucks and traditional SUVs typically retain body-on-frame construction. Modern crossovers (which look like SUVs but are based on car platforms) use monocoque. The Lamborghini Aventador, McLaren cars, and Pagani hypercars use carbon fiber monocoques (extreme weight savings combined with high stiffness). Most modern luxury and sport cars use steel or aluminum monocoque construction.