Galaxies are vast systems of stars, planets, dust, gas, and dark matter bound together by gravity. Galaxies come in various shapes and sizes. Each galaxy contains billions to trillions of stars, along with other celestial objects such as nebulae, star clusters, and black holes. Galaxies are the building blocks of the universe, forming clusters and superclusters that are interconnected through gravitational interactions. They play a crucial role in the evolution of the cosmos, serving as the birthplace of stars and providing insight into the structure and dynamics of the universe.