The 4 basic lights for portrait lighting are key light, fill light, hair light, and edge light. The key light is the primary light source and suggests an off-camera light. Fill light reduces shadows created by the key light. Hair light adds shine and separation from the background. Edge light defines the subject's outline. Background and accent lights can provide visual interest or separation in the background. Placement, quality (hard vs soft), and intensity of each light impact the overall mood and look.