What are some common applications of the MOV? (Metal Oxide Varistor)
A varistor after the fuse ensures that when the voltage crosses a certain value, the fuse blows and current flow stops. Generally fuses are rated for a current limitation, not a voltage limitation (as in your example). It is possible that the voltage difference across the fuse is such that it doesn't create more than the rated current through the fuse yet is still such that it could cause harm to harm the circuit (or is just unwanted). In that case the varistor is used to increase current through the fuse, causing it to blow and stop the current. When the voltage crosses the upper limit, the varistor resistance is reduced, increasing current through the fuse as in this circuit:



Many PCB circuits contain inductors and capacitors which will create transient states and surges (switching spikes). Too much of this kind of occurrence will harm the device, so varistors are used for protection.