The "Great Wall of Galaxies" refers to vast cosmic structures formed by clusters and superclusters of galaxies. These walls are part of the large-scale structure of the universe, where galaxies are not evenly distributed but instead form intricate patterns. One of the most well-known examples is the Sloan Great Wall, which is a massive galaxy filament discovered in the early 2000s. These walls can stretch for hundreds of millions of light-years and are separated by enormous voids, which are regions with very few galaxies. The study of these structures helps astronomers understand the formation and evolution of the universe, as well as the distribution of dark matter and dark energy.