Body treatment is a blanket term for a whole gamut of different holistic, non-medical, physical procedures aimed at helping you achieve something specific for your body. A "body treatment" could involve all sorts of things.
You might be:
massaged or scrubbed with a particular oil, cream or mineral
wrapped or enveloped in something - perhaps mud or seaweed or even plastic
immersed or soaked in a liquid, such as water or algae
stroked, treated with or exposed to something external - like brushes, magnets or electric current, or lights.