what is the different between getGeometry() and getCachedGeom()

Hi, everyone.

what is the different between getGeometry() and getCachedGeom()?

var oMale = Scene.findNodeByLabel("Genesis 8 Female");
var oObject = oMale.getObject();
var oShape = oObject.getCurrentShape();
var oGeometry = oShape.getGeometry();
print(oGeometry.getNumVertices());
var oVertexMesh = oObject.getCachedGeom();
print(oVertexMesh.getNumVertices());

result: 16556
        65806

why get different numVertices？