http://en.wikipedia.org/wiki/Dantian
"The Dan Tien or Tan t'ien literally means "cinnabar or red field" and is loosely translated as "elixir field". It is described as an important focal point for internal meditative techniques and refers specifically to the physical center of gravity located in the abdomen (about three finger widths below and two finger widths behind the navel). The dantian is important in Neidan, qigong, neigong, tao yin and other breathing techniques, as well as in traditional Chinese medicine. It is also widely used throughout East Asian meditation and martial art theories, especially the neijia school of Chinese martial arts and Tai Chi Chuan. Taoist and Buddhist teachers often instruct their students to center their mind in the dantian. This is believed to aid control of thoughts and emotions. Acting from the dantian is considered to be related to the state of samadhi." more ...

http://en.wikipedia.org/wiki/Sam%C4%81dhi_(Buddhism)
"In Buddhism, samadhi is mental concentration or composing the mind. In the Pali literature, samadhi is found in the following contexts: In the Noble Eightfold Path, "right concentration" (samma-samadhi) is the eighth path factor. Similarly, samadhi is the second part of the Buddha's threefold training: sila (morality or virtue), samadhi or samatha (concentration), and pañña (wisdom). In the development of the four jhanas, the second jhana is "born" from samadhi (samadhija). According to the Visuddhimagga, samadhi is the "proximate cause" to the obtainment of wisdom." more ...