The figure exhibits the vacuum clutch mechanism. This type of clutch employs the present vacuum inside the engine manifold to function the clutch. The vacuum clutch is made of a reservoir, non-return valve, vacuum cylinder with piston, and solenoid valve.  But let us stick with the topic of vehicles these https://travisrrlfz.blogocial.com/the-definitive-guide-to-clutch-plate-68825008