CMB, or Cosmic Microwave Background, refers to the faint radiation left over from the Big Bang that occurred approximately 13.8 billion years ago. This radiation permeates the entire universe and is considered one of the most important pieces of evidence for the Big Bang theory. Studying the cosmic microwave background allows scientists to learn more about the early universe, the formation of galaxies and large-scale structures, and the overall evolution of the cosmos. Researchers use various instruments and techniques to observe and analyze the CMB in order to better understand the nature and history of our universe.