As far as I know there are 4 different kind of PHs.
- single stational PH,
- double stational PH,
- single moving step PH,
- double moving step PH.
Clip is always better than words.
http://www.youtube.com/watch?v=lZwMhfF1SRc
It's very pleasent to watch Su Dong Chen's clip. This is the kind of performance that I'll expect from any Taiji master. He does not just think about 1 point "push" as others. He punches, kicks, locks, and throws. Not only he understand multiple points contact concept, he also understand how to "finish (such as kick his opponent's head on the ground)" that you just don't see in many Taiji "push (see you later)" clip.
http://www.youtube.com/watch?v=-MF7u0RhPlg