Basic idea about Galaxy, Star and Nebula
The beauty of the twinkling stars high above in the endless expanse of the sky, has charmed us for ages. These stars group together to form "Star islands" or "Galaxies". In other words, a galaxy is a cluster of stars in the outer space. It is so big that it is sometimes called "Island Universe". Each galaxy is a gravitationally bound system of millions of Stars and Nebula and the Universe is thought to be built up of millions and billions of such galaxies. Star and Nebula are two different types of astronomical objects. A Nebula is a cloud of dirt and dust and gas from which stars are born. Whereas, a star is a luminous celestial body of spherical shape, made up of plasma, hydrogen, helium, etc.
The word galaxy is derived from the Greek word "gala" or "galakt", meaning "milky", as it looks like a milky band of light in the sky. Galaxies range in size from "dwarfs" with just a few hundred million stars to "giants" with one hundred trillion stars, each orbiting its galaxy's center of mass. It is considered that, there could be one hundred billion galaxies in the universe, of all sizes, shapes and colours.
The Sun is a star and our Earth, a planet, is one of the members of sun’s family, known as "Solar Family" or the "Solar System". In Greek, the word "sol" means "sun" . Thus, the word "solar" means, anything pertaining to the Sun.
So the solar system is the name astronomers give to the Sun and the group of heavenly bodies that revolve round it systematically.
The solar system belongs to a galaxy known as the "Milky way". In India it is known as "Akash Ganga". The members of the solar family are the sun, eight planets and their natural satellites, dwarf planets, thousands of asteroids, a few comets and swarms of meteors.