A collection of stars, gas, and dust in space is called a galaxy. Galaxies come in various shapes and sizes, containing billions of stars, along with planetary systems, nebulae, and other celestial bodies. The Milky Way, for instance, is the galaxy that contains our Solar System. Galaxies are fundamental components of the universe and are often bound together by gravity. They can range from small dwarf galaxies to massive ones, exhibiting intricate structures and dynamics that astronomers study to understand the cosmos better.