SDSS, or the Sloan Digital Sky Survey, is a large-scale astronomical survey that has been ongoing since 2000. It aims to map and create a detailed three-dimensional map of the universe, including galaxies, quasars, and stars. The survey uses a dedicated 2.5-meter telescope located at Apache Point Observatory in New Mexico, along with a variety of instruments to collect data on objects in the sky. SDSS has made significant contributions to our understanding of the structure and evolution of the universe, including the discovery of new types of galaxies and mapping the large-scale distribution of matter.