A Penrose diagram is a graphical representation used in the field of general relativity to illustrate the causal structure of spacetime. It simplifies complex spacetime geometries, allowing physicists to visualize the relationships between different events, such as the formation of black holes or the behavior of light rays. These diagrams map infinity to a finite region, making it easier to analyze the behavior of objects and light in extreme gravitational fields. By using a conformal transformation, Penrose diagrams help depict how time and space interact, providing insights into the nature of the universe and the limits of our understanding of black holes and cosmology.