Extrema, Maxima and Minima

These are the plural forms of the words "Maximum" and "Minimum". Both of them are an Extremum. An extreme part of something, the biggest and smallest.

They mean exactly what you think they mean.

For a given set A, the maximum and minimum of this set A, denoted by represent, respectively, the largest and smallest element of this set.

This serves as a prelude to the next topic:
Bounds and Boundedness