Cybernetics is the technical term for studying communication systems and for checking control systems, such as regulation of clocks, waterworks, etc. In biomedical terms, it means the study of how various neural and other biological components of the body communicate with each other.
You will find a cybernetics expert or researcher involved in molecular biology research using complex set of cells or molecules to study how they communicate with each other, what messages are passed on and so on. In biomedical sciences, this study is particularly important to study why certain persons suffer from personality deficits, psychological defects, hearing defects, neural defects, and what causes paralysis, permanently, or partially, and how the cognitive systems, such as the sense of smell, sight, hearing are inter-related, and how the neural system (the brain and other areas) receive, absorb, co-relate, and issue commands to other parts of the biological systems to respond in particular manners, or how does one cell simply does not communicate, but allows it to pass through.
A simple example that would illustrate this idea is the sense of burn. When you touch a hot surface, the immediate reaction, involuntary it is because you do it unconsciously, is that the limb touching the hot surface immediately retracts. Thus a signal has passed from the multitude of cells that constitute the skin of your hand to transmit it instantaneously to the brain that something that was not expected or is dangerous to the skin has occurred, and the brain in turn signals the withdrawal of the hand from that area, without conscious action on your part. Thus in this manner, the signals that have passed from the brain to the hand, and from the hand to the brain are part of the biology cybernetics.
Study of cybernetics has led to the modeling and use of robots in industrial and other fields.
It is used in your water heaters, your meal cookers, your cars (ignition timings, speed control), and in so many more. Another useful technique that is coming up and is due to cybernetics is the ability of the motor car to sense another in proximity and to apply the brakes even before you can react! It is extensively used in artificial intelligence, and of course on this computer you are using to read this article.