The GeometryOverlay function takes two geometries described by the well-known text (WKT) markup language and outputs the result of overlaying them, as specified by the boundary operator.
You can use this function to prepare sets of geometries for input to the PointInPolygon function. For example, you can use this function to prepare a geometry that contains all cellular phone reception polygons near an airport to create a geometry that is useful for identifying frequent fliers.
The function works only on 2D spatial objects.