what about this picture/function/expression?
well, we have 3 points over the y-coordinate, but but but, every point has the same x-coordinate, whatever that might be, and so they form a vertical line.
does this straight vertical line pass the vertical line test? nope.
other way to see it is, a function has no x-repeats, the x-coordinate for every point must not be repeated, in this case it is the same for all, so it repeats thrice, so is not a function, just a relation.
