You will begin to feel that your taijiquan practice goes beyond simple form training, and you will be able to perceive things as energetic combinations, rather than as static physical objects. Your training partners will appear to your senses as dynamic patterns of energy, rather than as clumsy physical bodies. When this happens, you can skilfully switch strategy and tactics in any situation.
 
 (Yang Jwing-Ming)

Projection

http://www.youtube.com/watch?v=t3v-W1cPeGI

Neigong & jing

The internal arts all employ whole-body strength (neigong) rather than conventional muscle usage.
Whole-body strength was designed to amplify the effect of your actions whilst reducing the effort involved.

This enables the exponent to generate internal power (jing).

Pandora's Box

Years ago, I made the mistake of asking Sifu to show me a 'projection' and found myself pitched across the room.
The application wasn't painful at all.
In truth, I never even felt it.
I landed in a heap on the floor before I knew what was happening.
Everything went "Crunch!"

The truth is that I wasn't ready for it. My body wasn't ready for it. My nervous system wasn't ready either.
I lay on the floor and wondered if I was ok.

Sifu will sometimes indulge a student's curiosity, but this is not always a good thing for the student.