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And the "Sub" frame is the bars welded within the frame itself.

No. There are several different ways to make a car chassis.
The old way, and the way that trucks are built, uses a steel frame to hold all of the mechanical drive components and suspension. The body is mounted to that. The sub frame is used on unitized body's to hold these components, usually one in the front and another in the rear.
The chassis refers to the entire mechanical assembly that holds all the drive line and suspension components. In the case of a car with a frame that would be the frame and all the parts attached, less the body.

the frame is the main body of the vehicle that is bolted onto the chassis.

In the case of vehicles, the term chassis means the frame plus the "running gear" like engine, transmission, driveshaft, differential, and suspension. A frame is a structural system that supports other components of a physical construction. A subframe is a structural component of a vehicle, such as an automobile or an aircraft, that uses a discrete, separate structure within a larger body-on-frame or unit body to carry certain components, such as the engine, drivetrain, or suspension. The subframe is bolted and/or welded to the vehicle. When bolted, it is sometimes equipped with rubber bushings or springs to dampen vibration.

is car chassis, frame, subframe, all the same

thing? if so whats the difference?

cars have not had a full chassis for many years.a full rail chassis runs nearly the full length of the body..these days a sub frame is used to mount the motor and gearbox on.the sub frame runs fromthe front bumper to just under front seats.
i believe they use full chassis on big four wheel drives for extra strength when off road and extra weight they carry..hope that answers your question..