A suspension is a system of linkages that connects the chassis of the vehicle to the wheels. its primary purpose is to keep all wheels in constant contact with the ground,thus ensuring stability and proper tration of the vehicle. The suspension can also isolate the chassis from bumps and vibrations generated by the ground-but this is actually its secondary function, and it's not even present in all types of suspensions.
In order to maintain stability, a vehicle needs to be suported at no fewer than three point. For example, a bicycle is supported at just two point-where its wheels touch the ground-and it will fall over unless you support it at another point or drive it fast, in which case the stability comes from the gyroscopic effect of a wheel,s rotations. So a vehicle needs at least three point of support, and we'll call these points fulcrums in our suspensions. Sometimes they are simply called point-hence the name 3 points-hence the name 3-point suspension for a suspension for one that provides four.