How does map scale affect cartography?

The scale of a map is the ratio of a distance on the map to the corresponding distance on the ground. This simple concept is complicated by the curvature of the Earth's surface, which forces scale to vary across a map. Because of this variation, the concept of scale becomes meaningful in two distinct ways.

Explanation:

they are both the same distance away from the equator and from the poles. both circles are at 66 1/2 degrees. also they both form imaginary line borders of polar regions.