|Style over substance|
Mind-body woo is the idea that the mind, through mere thought, exercise, meditation, or other methods, can tangibly alter the body or the universe. There are some sensible interpretations (e.g., the placebo effect) and tons more woo.
 Sane stuff
The most well-received explanation for the mind over body argument is the release of adrenalin into the body, which does increase strength and endurance. Basically the body's abilities are underappreciated, so that exceptional feats brought about by "mind over body" are seen as mysterious or even paranormal.
 Hot coals
Of interest is the fact that the Mythbusters tested whether walking on hot coals is a "mind over matter" thing. The conclusion was that the ash formed a layer over the hot coals, which actually allowed you to safely walk across the fire. Adam Savage, however, sustained second degree burns to his foot because he panicked halfway across the path, and disturbed the ash layer.
 Hair standing on end
A more moderate approach would be to say that, for example, you can consciously make your hair stand up on end. Some people can exercise an amount of conscious control over their heart rates, or "tick" muscles that are not normally used. You can even use biofeedback to learn how to do this.
The more extreme aspects of the mind-over-body concept argue that the defiance of the body's limits demonstrates an innate potential that our body is masking, similar to Scientology. While indeed the body can do impressive things, and holds secrets we do not know about, the extremes that people think of are almost certainly impossible, according to every known law of physics. For example, it is physically impossible to lift things without touching them, though it is possible to lift a 500 pound log without injury (just unlikely).
At the less realistic end of the scale is the sort of claims seen in New Age philosophies that positive thinking can override both the body and even physics itself — such as the claim in New-Age-Luvvie-Fest What the Bleep Do We Know? that "if you believe it with all your heart, you can walk on water."