Water pressure (like PSI) and how it relates to water flow (like GPM). It's difficult to relate the two together and even after hearing every heuristic and eve

Water pressure (like PSI) and how it relates to water flow (like GPM). It's difficult to relate the two together and even after hearing every heuristic and every cutesy analogy, I still can't quite wrap my head around what happens to one when I increase the other (and so on).