Contains

One spatial object contains another spatial object if its interior includes all points of the other object. If an object such as a point or linestring only exists along a polygon's boundary, the polygon does not contain it. If a point is on a linestring, the linestring contains it; the interior of a linestring is all the points on the linestring except the start and end points.

Contains(a, b) is spatially equivalent to within(b, a).