For instance, Along one portion of a path that the slope could be positive and becoming more positive. On this portion, you are walking up hill and the slope is increasing. On yet another portion of the path, the slope could be negative. So as your walking along, the height of the path is decreasing. Now as you walk along this downhill portion of the path, the slope may become more negative or less negative.
Positive slope corresponds to going up while negative corresponds to going down.
Moreover, and this is whether matters become complicated, the slope in changing may increase or decrease. Here a positive slope may increase by becoming more positive and a negative slope may increase by becoming less negative. Likewise, a positive slope may decrease by becoming less positive and a negative slope may decrease by becoming more negative. And in all these cases, the steepness or slope of the curve changes. The steepness is given by the absolute value or magnitude of the slope.