Long time ago, but mathematical functions. In hindsight stupid, but it took me embarrassingly long to understand that a function just takes a value for x, calc

Long time ago, but mathematical functions. In hindsight stupid, but it took me embarrassingly long to understand that a function just takes a value for x, calculates it with the rest of the numbers in the function and that way basically assigns a y-value to every x-value. No idea why it took me so long, I didn't have any similar problems with high school math