Asteroids, sometimes called minor planets or planetoids, are small Solar System bodies in orbit around the Sun, especially in the inner Solar System; they are smaller than planets but larger than meteoroids.
A comet is a Small Solar System Body that orbits the Sun.
A nebula (from Latin: "cloud"; pl. nebulae or nebulæ, with ligature or nebulas) is an interstellar cloud of dust, hydrogen gas, helium gas and plasma.
The Solar System[a] consists of the Sun and those celestial objects bound to it by gravity, all of which formed from the collapse of a giant molecular cloud approximately 4.6 billion years ago.