A diverter simply takes the flow from one set of hydraulic hoses and splits them into two sets. When the switch is off, the fluid simply goes through the diverter to one set, when the switch is on, the fliud goes to the other set. You can only use one set at a time.
I just added one to my FEL to operate the angle on a snowplow that I built.
Check this POST to see pics of my setup. Although the JD one will look different and be more hidden, the theory is the same.