Enclosed regions of the path alternate between interior and exterior areas as traversed from the outside of the path towards a point inside the region.

WINDING_

If a ray is drawn in any direction from a given point to infinity and the places where the path intersects the ray are examined:
The point is inside of the path if and only if the number of times that the path crosses the ray from left to right does not equal the number of times that the path crosses the ray from right to left.