Galactic structures refer to the various formations and arrangements of matter in the universe, primarily focusing on galaxies, star clusters, and nebulae. These structures can range from individual galaxies, like the Milky Way, to vast clusters containing thousands of galaxies bound together by gravity. Understanding galactic structures helps astronomers learn about the formation and evolution of the universe. For instance, the study of dark matter plays a crucial role in explaining how galaxies and clusters are held together. Observations of these structures provide insights into the cosmic web that connects galaxies across vast distances.