It's a technique that focuses on manipulating your natural energy. Some people use it to develop their concentration or self-control, but it can be used to focus your energy for martial arts, too.

[He sits forward again, picking out the videocasette and sliding it in, staying by the VCR to fiddle with the fast-forward buttons. The VCR might once have had a remote, but by the time Hakkai had purchased it, that was long missing.]

All of the practice certainly did help me learn to use my chi later!