Chassis can mean two different things in automotive engineering.
A chassis is a structural frame which carries mounting points for the suspension and drivetrain, onto which a body is mounted. Though most modern cars do not use this form of construction, it is still used in commercial vehicles, 4x4s and some specialist vehicles. Most modern cars have unitary construction where structural members - often known as 'chassis members' - are built into the body.
Chassis is also used to denote the running gear of a vehicle. A 'chassis engineer' works on ride, handling and braking.
