The difference between an asteroid and a comet lies primarily in their composition and origin. Asteroids are rocky, metallic bodies that predominantly reside in the asteroid belt between Mars and Jupiter. They consist mainly of minerals and metals. Comets, on the other hand, are composed of ice, dust, and rocky materials, originating from the outer regions of the solar system, such as the Kuiper Belt and the Oort Cloud. When comets approach the sun, they develop a glowing coma and tail due to the sublimation of their icy components.