Dimmer switch, Some even come with a remote! First find the breaker and flip the switch, cutting power to the switch. remove the old standard switch with a screw driver and some care. Black wire is the hot line, white is the neutral, green is ground. The dimmer switch will have the proper markings on the back plate, match up the corresponding wires, usually you will push the copper lines into the back of the switch so no screwing the lines onto a connection plate. ground is to protect the surface so find the green screw and once you replace the switch with the two screws into the wall, add cover plate and you have your " mood lighting" dimmer switch. Good luck and enjoy.