The appropriate definition of a solar system can be:- "Collection of planets revolving around a star. In our solar system, there are eight planets, Sun and many other bodies revolving around Sun."The Solar System is consists of all the eight planets that circle our Sun. In addition to these eight planets, the Solar System also contains comets, moons, minor planets, asteroids, gas, and dust.
Image credit: Dr. Steuard Jensen
Everything that we can observe with or without the telescope in the Solar System orbits the Sun. In our Solar System, the Sun covers almost 98% of all the material. It is the universal law that the larger an object is, the more gravity it will have. Because the Sun is very large and massive, its dominant gravity draws all the other things in our Solar System towards it. During this pull of sun's gravity, all these things in our solar system, that are moving very rapidly, also attempt to glide away from the Sun outward into the desolation of external space. The outcome of the planets demanding to fly away, at the same time that the Sun's gravity is trying to tug them inward is that they get stuck half-way in between the sun and outer space and starts orbiting the sun and does not fall into the sun or gets out of the range of sun’s gravity. So they spend all time circling around their parental star in the case of our solar system it is the sun.
You might have heard about the Asteroid Belt. This is actually a band of asteroids that lies among the orbits of the planet Jupiter and Mars. It is consists of thousands of objects and these objects are too small to be considered as planets. Few of them no bigger than just a particle of dust, while there are some others, like Eros that can be larger in size more than even 100 miles across. A few of these asteroids, like Ida, even have their own moons.
If you go further than Gas giants, outside the orbit of the Dwarf planet Pluto, there is another belt that consists of icy bodies and known as the Kuiper Belt. Just like the Asteroid Belt, the Kuiper Belt is also consisting of thousands, maybe even millions of objects, which are too small to be considered as planets.
These objects in Kuiper belt and Oort cloud are made up of generally ice-covered gas with small quantities of dust. They are sometimes also known as dirty snowballs. Though you maybe know them by their additional name and that is comets.