...
Unibody: The frame and body are a single integrated piece. This is the most common design used on modern consumer cars. Steel unibodies form most of the body of the vehicle with an integrated steel structure and may have plastic paneling for aerodynamics.
Space frame: The vehicle has a skeletal frame constructed of steel beams or tubes of varying diameter and wall thickness. Non-structural panels are attached to the frame solely for aerodynamic purposes but otherwise provide no additional strength. This design is used on some high-performance consumer cars and smaller, older aircraft. The strict technical definition for a space frame is that the frame is sufficient triangulated such that all forces within the frame are turned into compression or tension, and not flexing.
...