A galaxy is a huge collection of stars, dust, and gas. Galaxies usually consist of up to a trillion stars. There are hundreds of billions of galaxies in the universe, in different shapes, sizes and brightness. Our planet, Earth, is part of the huge galaxy called the Milky Way. Our Sun and its planets are about half way out from the center. The sun orbits the center of the galaxy.
The Milky Way is shaped like a huge whirlpool that rotates once every 200 million years. It is made up of at least 100 billion stars, as well as dust and gas. It is so big that light takes 1000 years to cross from one side to the galaxy, the stars are close together, and the galaxy shines brightly. This is why the Milky Way looks patchy.