Hi all,
Chi, Ki or Qi, it's all the same.
If you take the time to learn Wing Chun, or Wing Tsun depending on the lineage you study you will learn Qi Gong, or how to harness that energy.
It is a good excercise to perform, but can cause you harm if you do it incorrectly, or for too long.
Basically you can compress the air in your lungs, and increase the energy / oxygen flowing through your body, the deep breathing involved stretches your adrenial gland to produce more and more adrenaline, thus increasing energy at your disposal.
Bruce Lee was great at this, hence the energy he could produce for his famed "One inch punch"
This is possible for all people to achieve, but to reach the same level takes years and years of dedication.
When you can learn to control your Qi, as Kevin states, you can "throw" balls of energy (obviously these are not viisible energy balls, although that would be cool!)
One small note to people who are just learning to control their Qi, try to remain as relaxed as possible at all times. If you find yourself, or a muscle tensing up (not that muscle) then stop straight away. I didnt know this when I started, and after over-doing it ended up having severe muscle spasms in my neck.
A good example of Qi control was Derren Brown visited the Wing Tsun school in london, and managed to knock a student clean off his feet without touching him, just by harnessing his own Chi.
Sorry to waffle on, just started posting, an now I CAN'T STOP!
Apologies & regards,
MrBen