Tightrope walking, also called funambulism, is the skill of walking along a thin wire or rope. It has a long tradition in various countries and is commonly associated with the circus. Other skills similar to tightrope walking include slack rope walking and slacklining. A funambulist maintains their balance by positioning their center of mass directly over their base of support, i.e. shifting most of their weight over their legs, arms, or whatever part of their body they are using to hold them up. Sometimes, a wire-walker may use a pole for balance or may stretch out his arms perpendicular to his trunk in the manner of a pole.

Source: Wikipedia