Question

Contours on maps indicate:

Answer 1

It helps to know the various height of the relief features

Answer 2

a contour line (often just called a "contour") joins points of equal elevation (height) above a given level, such as mean sea level. A contour map is a map illustrated with contour lines, for example a topographic map, which thus shows valleys and hills, and the steepness or gentleness of slopes.