I understand "premium" (what you always pay, whether you use it or not)

I think I understand "co-pay" (what you pay at point-of-use (unless you've hit your annual out-of-pocket maximum (unless you're out-of-network)))

I absolutely do not understand "deductible", which seems to mean something different every time I look at it.

And it gets more esoteric from there.

I usually just pay cash-on-the-barrel for healthcare. Most places do a "same day payment" discount that can be up to 40%.