In order to represent spherical features on a flat surface, we must use some type of projection. Projections stretch a map in some directions, shorten it in other directions.
Scale then varies from point to point.
Each projection is tied to one or two standard lines. On flat maps, the scale is usually consistent only along these lines. Scale distortion increases with distance from the standard line. This area around the standard line is called the area of least deformation. True shapes are sacrificed but the scale is the same within each quadrant.