Someone please tell me what the difference is between a flasher and a relay and why would you need to use a relay in the circuit with the flasher...

 

Google: automotive flasher vs relay. It explains everything.

 

In generic terms, a flasher is a relay that automatically turns on and off when power is applied. It automatically makes and breaks the power.

A relay will make and break the power, but only when told to do so by another small applied signal from another source.

So you could use a flasher to make and break the signal to a relay, which would make the relay turn on and off. Why would you do this? Possibly because the flasher was not large enough to handle the amount of bulbs in the circuit, the relay may be rated for a larger circuit.

Caution. Ford and other OEMS call components whatever they want to. They can have combinations of parts put into a single box, and call it whatever they want, a relay or a flasher module or a flasher relay. Why? Because it's their vehicle and they can call it what they want I guess.