The rendering pipeline is the sequence of stages that transforms 3D scene data into a 2D image on your monitor. The modern pipeline starts with the application stage (CPU submits draw commands), moves to geometry processing (vertex shaders transform vertices, tessellation adds detail, geometry shaders modify primitives), then rasterization (converting triangles to fragments/pixels), fragment shading (calculating color for each pixel using lighting, textures, and material properties), and finally output merging (depth testing, blending, writing to the framebuffer). Deferred rendering splits this into multiple passes -- first render geometry data to G-buffers, then apply lighting as a screen-space pass. Forward rendering handles lighting per-object but is simpler and better for transparency. Modern pipelines add passes for shadows, screen-space reflections, ambient occlusion, bloom, anti-aliasing, and post-processing effects, easily totaling dozens of render passes per frame.