  The cosmic microwave background (CMB) comprises the oldest photons in the
universe and is arguably our most direct cosmological observable. All precise
and accurate measurements of its attributes serve to distinguish between
cosmological models. Detector technology and observing techniques have advanced
to the point where fluctuations in the CMB of order a few microkelvin are
measured almost routinely. In these lecture notes, we review recent
measurements of both the absolute temperature and the anisotropy of the CMB and
discuss the relation between the data and the general theoretical framework.
Future directions are indicated and the upcoming satellite experiments are
discussed.
