One way of translation is "Life force cultivation", but the character qi can mean a whole bunch of things, from life force to energy to vitality. The character gong means practice or cultivation, it is the same character as kung in kung fu. Qigong is one of the four branches of Chinese medicine, the others being acupuncture, herbs and Chinese massage.

Qigong is self-healing, in a nutshell. It bears similarities to yoga, in that it uses mental concentration and body relaxation. There are thousands of qigong rituals, some as simple as lying down and taking a deep breath, others venture into strange and complex rituals. Shadow boxing, or Tai chi, is a form of qigong. Proper use of qigong can speed healing and refresh the body and mind, as well as remove the need for heavy doses of medicine. Qigong alone cannot heal major illnesses, but it can help a lot with the process.

Another facet of qigong is its use in the martial arts. Apparently, a fighter can mentally focus so intently that he forgets the body, and any pain inflicted on his person will be ignored. I've seen it happen a few times, like a person who got hit very hard repeatedly with a wooden staff all over his body and didn't even flinch. Maybe it was qigong, maybe it's not, I don't know. Bruce Lee was known to practice qigong to improve his stamina.