Help with "Track Event Dimmer" in RM

In the Control Dimmers section of Rule Machine, there is a toggle "Track Event DImmer?"
Can someone please explain what this is, and give me a use case?

I use wall switch/dimmers to indirectly control a Hampton Bay light/fan. The wall dimmers don't connect to anything (except power).

Rule basically says if the level of the wall switch isn't equal to the level of the light, then have the light dimmer track the wall dimmer. There's another rule which say if the wall switch is on, turn the light on, otherwise turn it off.

Similar for the fan.

But, you could also use it so multiple dimmers could all track a "master" dimmer.

So, it sounds like you could create a rule that would, for example, set all the dimmers in your house to the level of a "master" virtual dimmer device. How do you select which dimmer is the "master"?
Perhaps @mikes could show us your rule?

Sorry for the delay, don't get here much. I'm doing stuff differently now, but the rule was basically

Trigger: Dimmer level of Switch changed

Set Dimmer Level:Track Dim: Light