The job of a shower diverter is to redirect the water flow from the tub faucet spout to the shower head. Depending on the particular type of faucet and whether it has three handles, two or only one, you divert the water in different ways. To locate the diverter assembly itself, you will either need to remove a handle or the tub spout to find the diverter and its components underneath.
The diverter knob will either be a handle or a knob that you twist a certain direction to divert the water from the tub to the shower or is a valve on top of the tub spout that you pull up and push down to divert the flow of water.
The actual diverter valve is found behind the knob that you turn to divert the water or behind the tub spout with the valve atop it. The actual body of the diverter is a stem-like diverter, a diverter with a spring inside it or a cartridge-type diverter. The specific type of diverter out of those three that is used depends on the type of faucet that is installed in the shower.
O-rings and Washers
The diverter has an O-ring, a washer or a combination of both that serve to provide a seal to direct all the water either up to the shower head or down to the tub spout. The particular location of the O-rings and washers on the diverter depends on the specific type of diverter used.