A disco ball (also known as a mirror ball or light ball) is a spherical object that reflects lights in many directions, creating complex light manifestations. Its surface consists of hundreds or thousands of flashes, almost all of approximately the same shape and size, everyone with a mirror surface.
It is usually mounted above the heads of the people, suspended from a device that make a rotation along a vertical axe and is illuminated by projectors. This effect for the spectators is the presence of light flashes and spots above them  (similar to created by natural light sun bunnies) by light that revolve around the walls of the room.