Bio-feed-back – as it is seen from the three parts of the word Bio – is biological, which means natural for the given biological system; Feed – means providing the resources to fulfill the needs; Back – means “in response”: something is happening first and “in response” or “back” the second action occurs. To apply the statements above to the biofeedback it is clear now that being open system living body constantly exchanges the information with the outer space in form of energy. Giving the information about inner systems out it listens for the information from the outer space. When the right “readable” information comes, the body accepts and applies it to the inner systems. Biofeedback devices are built on principles of opened inter- communicative systems described above. Certain areas on the surface of the skin are providing the information about inner organs and systems. Biofeedback device reads this information and according to its programs interprets the information comparing it with the standard algorithm for the normal functioning body. If the information differs from the normal one, it means that something is wrong in the inner system. In this case the device generates “right” impulses and sends them back to the inner system to improve it. This is very simple and very basic explanation how the biofeedback works. For more information you can refer to