THE CREW - Lighting Department 

"The gaffer is basically the cinematographer's right-hand man. He is in charge of the lighting crew to illuminate exteriors and interiors." Yves Bernadet, Gaffer
The Lighting or Electric Department is responsible for the lighting of any scene. The Lighting Department is also responsible for supplying power to the filming unit while it is on location.
Positions discussed in this episode:
Gaffer: The head of the lighting and electrical departments on-set. S/he determines electrical and power requirements, and oversees all electrical aspects of the production, particularly those associated with lighting.
Best Boy: Next in command to the gaffer. In charge of ordering equipment and loading vehicles used by the lighting department, and responsible for having on-set all equipment and personnel required by the lighting department.
Lamp Operator: A technician who sets the lights and related equipment under the direction of the gaffer.
Generator Operator: Also known as the "genny op" - the person responsible for the proper running and maintenance of the power generator on set.