The first record of Acupuncture is found in the 4,700 year old "Huang-di Nei-Jing" (Yellow Emperor's Classic of Internal Medicine). This is said to be the oldest medical textbook in the world, written down from even earlier theories by Shen Nung, the father of Chinese Medicine. Shen Nung documented theories about circulation, pulse and the heart thousands of years before European medicine had any concept of them.
Shen Nung theorized that the body had an energy force running through it, known as qi (roughly pronounced: Chee). Qi travels throughout the body along meridians (or channels), in a similar way as blood and nerves, for instance, run through the body.
There are fourteen main meridians running vertically up and down the body and energy constantly flows up and down these pathways. When the pathways become obstructed, deficient, excessive, injured or just unbalanced, the body is seen to be thrown out of balance, and this causes illness, or symptoms of illness.
The acupuncture points are specific locations on the meridians, which are accessible by 'needling', moxibustion.