A gaffer is the head electrician on a film or television set, responsible for the lighting design and execution. They work closely with the director of photography to create the desired mood and atmosphere for each scene. Gaffers manage a team of electricians and ensure that all lighting equipment is set up and functioning properly. In addition to lighting, gaffers also handle the placement of various lighting instruments, such as LED lights, floodlights, and spotlights. Their expertise is crucial for achieving the visual style of a production, making them an essential part of the filmmaking process.