  These lecture notes form a primer on the theory of cosmic microwave
background (CMB) anisotropy formation. With emphasis on conceptual aspects
rather than technical issues, we examine the physical foundations of anisotropy
evolution in relativistic kinetic and perturbation theory as well as the
manifestation of these principles in primary and secondary anisotropies. We
discuss gauge choice and gauge invariance and their use in understanding the
CMB. Acoustic, gravitational redshift and ionization effects have robust
signatures in the CMB spectrum and may allow determination of classical
cosmological parameters as well as reveal general distinctions between models
for structure formation. We develop the tight and weak coupling approximations
as analytic tools to help understand these effects and the robustness of their
signatures.
