I.J. Good: "Let an ultraintelligent machine be defined as a machine that can far surpass all the intellectual activities of any man however clever. Since the design of machines is one of these intellectual activities, an ultraintelligent machine could design even better machines; there would then unquestionably be an "intelligence explosion," and the intelligence of man would be left far behind. Thus the first ultraintelligent machine is the last invention that man need ever make, provided that the machine is docile enough to tell us how to keep it under control."

A merely human-level AI is one that can match to some window of performance a random human in the intellectual outputs of that human, which are vast and general -- playing games, writing poetry, critiquing film, building small rockets, having conversations, programming, carving wood, teaching a class, diagnosing and fixing a leak, constructing mathematical models... For things that require a body, it suffices to instruct a human what to do, but this thing might as well help design a robot body that's at least as versatile as a human body since we humans do that too even if Atlas is still pretty far off. We're unlikely to have an AI perfectly human-equivalent in the sense that it would probably by default already be superior in some ways by virtue of its ability to not need sleep, do calculations efficiently and correctly, have access to perfect memory, and so on, and unless it's ultraintelligent then it's probably not better than a random human at everything (say directing a movie) just like you aren't.