The cosmic microwave background radiation

We summarize the theoretical and observational status of the study of the Cosmic Microwave Background radiation. Its thermodynamic spectrum is a robust prediction of the Hot Big Bang cosmology and has been confirmed observationally. There are now 75 observations of Cosmic Microwave Background anisotropy, which we present in a table with references. We discuss the theoretical origins of these anisotropies and explain the standard jargon associated with their observation.