Let's put it this way: within the concept of "rolling a d20," I've seen in Actual Published Games, just off the top of my head without looking stuff up:
- Roll 1d20 and add a character/circumstance-based positive or negative modifier, aiming to meet or exceed a target number.
- Roll 1d20 and add a character/circumstance-based positive or negative modifier, aiming for *under* a target number.
- Roll 1d20 and check if it's even or odd, and whether it's rolled above, below, or exactly any combination of 1, 5, 11, 15, and 20.