Amongst these little gizmos, this is one of the more complicated of the lot. This device is actually two separate systems; upon its side are two "PC female" sockets, and upon the top is a "hot" shoe.
The very bottom of the device has a "hot" button, which is used to trigger anything attached to the bottom PC female socket when the entire device is inserted into a camera's hot shoe and that camera is fired. Whatever cord you would use to trigger a flash from the bottom PC female socket would need a "PC male" connection on one end, and whatever connection interfaces with your flash upon the other.
The top of this device also has a PC female socket, but that socket is not activated merely by placing the entire device into a camera's hot shoe and firing the camera. Instead, the top PC female socket fires the hot shoe which is on top of the unit. With cameras that have both a PC female connection and a hot shoe, this device allows you to simultaneously trigger two flashes---all by reliable cords!
To simultaneously trigger two flashes with one camera, simply connect a flash to the top of this device and attach a "PC male to PC male" cord between the top PC female socket upon this device and the camera's PC female socket to make the flash upon the top of this device fire (a small PC male to PC male cord is included). For your second flash to fire, first attach this device to the camera's hot shoe, then use a PC cord to attach the bottom PC female socket of this device and your flash. A straight or folding flash bracket such as the two listed here makes for a sensible accessory in this regard.