A Penrose diagram (conformal diagram) uses a conformal transformation to compress all of infinite spacetime into a finite square or triangle, preserving the causal structure exactly. Light rays always travel at 45° in these diagrams, making causal relationships immediately visible. The Schwarzschild black hole has four regions: exterior, interior (black hole), white hole, and a second exterior — only the exterior is accessible to distant observers. The singularity appears as a spacelike horizontal line, showing that once inside the horizon, hitting the singularity is as inevitable as the future itself.