The Chassis is the main body and structure of the car. There is no purpose of building a car without it having a chassis. And its impossible...

...however apart from that, it has a purpose too. It also allows for the connection of the wheel axle, suspension, yaw rods (for VSA or VSP/ whichever you know), etc.

Hope my answer helped.

get a chiltons repair manual from the library for your car.

where is the engine number located on the engine block

The chassis part of the car was prepared first. This is a sentence which contains the word chassis.

The chassis is the frame of the car.