How do lines show steep and gentle slopes?

Answer 1

Contour lines are lines that join up points on a map that represent points on Earth's surface that have equal height. The distance between the contour lines gives an indication of how much the height changes over a horizontal distance. In other words it shows you how steep or gentle the slope is.

As such a steep slope will be marked by closely spaced contour lines and a more gentle slope will have more widely spaced contour lines.