Another huge thing in Calculus is finding relative extrema.
Check out this graph:
The tops of the mountains are relative maximums because they are the highest points in their little neighborhoods (relative to the points right around them):
Suppose you're in a roomful of people (like your classroom.) Find the tallest person there. (It's usually a guy.) He is the relative max of that room. Specifically, he's the tallest, relative to the people around him. But, what if you took that guy to an NBA convention? There'd be lots of guys who beat him.