Classification of a Comet
You've answered your own question there, the difference between the two is that asteroids are rock whereas comets are made up of ice and dust.  An asteroid doesn't heat up when it gets close to the Sun and doesn't produce a tail.  Comets can orbit the Sun or any star in a long elliptical (Comet West) or short elliptical (Comet Encke 3.3 Years) period whereas asteroids are found in the Asteroid Belt between Mars and Jupiter and in the Kuiper Belt.  Sedna is a long period asteroid further out any other object in the solar system but it is still an asteroid according to what we know. https://www.universeguide.com/fact/comets  https://www.universeguide.com/fact/asteroids