Please be gentle and explain things as if you were talking to a six-year-old...

With my recent experience with a bass cut circuit with humbuckers, I've also been looking into simple high-pass filters.

I have used a passive RC filter before on neck humbuckers before but my understanding of how it works is rudimentary at best. My application is a parallel capacitor and resistor used in series with the pickup output.

I have experimented with the capacitor values and know on a very basic level that the lower the cap value, the more high frequencies will pass (or low frequencies filtered out).

What I would like help with is the role of the resistor in this application.
In very simple terms (remember I'm a six-year-old) what will increasing or decreasing the resistor value do to the operation of the circuit, and how will it effect the tone?

I've read something about "cut-off threshold" or something, but when I read that stuff, my vision gets blurry and my brain misfires...

Let me know if you need more info from me ie: pot/cap/resistor values etc.