A decade ago, Arri lens specialist Art Adams coined the terms paycheck stops and gravy stops.
Paycheck stops are values that you can bet your paycheck on. They’ll appear in the image with enough contrast and detail that objects exposed at that value will be easily discernible.
Gravy stops are the values that lie beyond paycheck stops: they are the tonalities at either end of the dynamic range scale where some presence will be seen, along with some discernible detail, but they shouldn’t be trusted. If there’s some information held in those tones then that’s great, but don’t count on it.