Also known as "Daylight Harvesting", daylighting is an electric control strategy that effectively dims the electric lights when more sunlight is let in the room. To speak plainly, the goal is to maintain a consistent brightness at a location. Sensors are required for this to measure the brightness or what is technically called the luminous intensity. These sensors typically measure the luminous intensity at desk level (approximately 2.5-3 feet). Daylighting has a direct savings on lighting, and an indirect savings on air conditioning, as well as fan energy in VAV systems.
Example:
A room that has windows and skylights, and is occupied during the day is an excellent candidate for daylighting. In energy modeling, a number of defaults are typically used when calculating daylighting because there are so many variables that impact luminous intensity (amount of glass, glass locations, wall heights, sensor locations and more)