Yippee!
They remembered Home Lock! Awesome!
HL works like a "headless" quad. Regardless or bird orientation, forward stick moves the bird away, backward stick brings her back. With the P2, this only works when the bird is more than 20 meters away, then the bird circles the home point.
POI is for circling a point and maintaining a certain distance away.
GS is for setting waypoints and the Phantom will follow the route with no input from the transmitter.