The slope of an area will determine the problem that you will be able to make, whether it is an even or a steep slope.
Examples of slope: http://www.answers.com/topic/slope http://en.wikipedia.org/wiki/Slope
The area with the steepest slope is the area where the contour lines are bunched closest together.
m stands for modulus, and is a measure of the slope.
The closer the contour lines the steeper the slope.