Spiral galaxies are a type of galaxy characterized by their distinct spiral arms that wind outward from a central bulge. These arms are made up of stars, gas, and dust, and they often contain regions of active star formation. The Milky Way is an example of a spiral galaxy, showcasing a beautiful structure with its own spiral arms. The central bulge of a spiral galaxy typically contains older stars and may harbor a supermassive black hole at its core. Spiral galaxies can vary in size and brightness, and they are classified into different types based on their structure, such as Sa, Sb, and Sc categories, which indicate the tightness of their spiral arms.