extrema means maxima and minima which are points where a function reaches a highest or lowest value, respectively. There are two kinds of extrema global and local, sometimes referred to as "absolute" and "relative", respectively. A global mensmaximum is a point that takes the largest value on the entire range of the function, while a global minimum is the point that takes the smallest value on the range of the function. On the other hand, local extrema are the largest or smallest values of the function in the immediate vicinity.
