The Penrose process extracts energy from a rotating (Kerr) black hole via its ergosphere — a region outside the event horizon where spacetime is dragged so fast that nothing can remain stationary. A particle entering the ergosphere splits: one fragment falls with negative energy (as seen from infinity) into the black hole, while the other escapes with more energy than the original particle carried. The black hole loses angular momentum in the exchange. Maximum extraction efficiency reaches 20.7% for a maximally spinning hole (a = M). This mechanism may power relativistic jets in quasars and active galactic nuclei.