The Cold Shoe is a bracket on top of a mounting plate or block. The mounting block is designed to be placed on a light stand, tripod or similar. A cold shoe is for holding an off-camera flash unit which is being used remotely from the camera. The cold shoe lacks any power of its own (hence ‘cold’ shoe). The lack of power and detachment from the camera define the difference from the hot shoe on the top of the camera. Thus, the cold shoe cannot trigger the flash on its own. The flash must have some method of receiving an impulse from the camera. Normally this is a radio signal or an impulse down a direct wired connection.
Cold shoes may have a wired internal connection. This will allow a wire to be directly connected from a camera to the cold shoe. The flash makes contact with this internal connection via the contact placed centrally on its foot where it fits into the cold shoe.
The cold shoe may be used to mount a variety of other accessories on light stands or tripods. These may include a radio-trigger receiver to fire a flash on a signal from the camera. Other accessories may include microphones for video recording and LED lights.
Cold shoes come in a variety of designs. The ones shown here have an internal wire so you can connect the flash to the camera by wire. Others may just be a bracket or they may simply look different to those shown here. Be aware of the wide design variations.