A giant galaxy is a large collection of stars, gas, dust, and dark matter bound together by gravity. These galaxies can contain billions to trillions of stars and can span hundreds of thousands of light-years across. Examples of giant galaxies include the Milky Way and Andromeda. Giant galaxies are often classified into two main types: elliptical and spiral. Elliptical galaxies have a smooth, rounded shape, while spiral galaxies have distinct arms that wind outward. The study of giant galaxies helps astronomers understand the formation and evolution of the universe.