It is all related to the perimeter. Perimeter is synonymous with edges, limits, border, outline, periphery, shore. In mathematics or better yet in geometry is the sum of the sides of a polygon.
The relevance to the perimeter. What measures a surface whatever its shape, square, Rhombus, rhomboid, trapezius, triangle, etc. Regardless, it would be anything contour measurement metrics.
Relative to the perimeter. Perimeter: what separates an object from its environment, outline of the object.