Walking on two feet, also known as bipedalism, is a form of locomotion in which an organism moves by means of its two rear limbs or legs. Bipedalism is a form of terrestrial locomotion where an organism moves by means of its two rear limbs, or legs. It is a common form of locomotion among animals and is one of the defining characteristics of the human species. Bipedalism is an adaptation that has allowed humans to become one of the most successful species on the planet.