Photon Mapping is a technique used in computer graphics to simulate the way light interacts with surfaces. It involves two main steps: first, photons, which are particles of light, are emitted from a light source and stored in a data structure. This helps to capture how light bounces around a scene, including reflections and refractions. In the second step, the stored photons are used to calculate the color and brightness of surfaces when rendering the final image. This method allows for realistic lighting effects, such as soft shadows and caustics, making scenes look more lifelike and visually appealing.