  The tremendous experimental progress in cosmic microwave background (CMB)
temperature and polarization anisotropy studies over the last few years has
helped establish a standard paradigm for cosmology at intermediate epochs and
has simultaneously raised questions regarding the physical processes at the two
opposite ends of time. What is the physics behind the source of structure in
the universe and the dark energy that is currently accelerating its expansion?
We review the acoustic phenomenology that forms the cornerstone of the standard
cosmological model and discuss internal consistency relations which lend
credence to its interpretation. We discuss future milestones in the study of
CMB anisotropy that have implications for inflationary and dark energy models.
These include signatures of gravitational waves and gravitational lensing in
the polarization fields and secondary temperature anisotropy from the transit
of CMB photons across the large-scale structure of the universe.
