A galaxy is a collection of stars and planets that are held together by gravity. In a galaxy, the celestial bodies rotate around a central object.
The Earth's galaxy is known as the Milky Way. Our solar system, made up of the Sun and the planets that encircle it, is a tiny part of that galaxy. A galaxy can also refer to a gathering of a lot of sparkly people –– like celebrities or sports stars. What gravity holds this galaxy together? Usually cameras.