  The Wilkinson Microwave Anisotropy Probe (WMAP) mapped the distribution of
temperature and polarization over the entire sky in five microwave frequency
bands. These full-sky maps were used to obtain measurements of temperature and
polarization anisotropy of the cosmic microwave background with the
unprecedented accuracy and precision. The analysis of two-point correlation
functions of temperature and polarization data gives determinations of the
fundamental cosmological parameters such as the age and composition of the
universe, as well as the key parameters describing the physics of inflation,
which is further constrained by three-point correlation functions. WMAP
observations alone reduced the flat $\Lambda$ cold dark matter ($\Lambda$CDM)
cosmological model (six) parameter volume by a factor of >68,000 compared with
pre-WMAP measurements. The WMAP observations (sometimes in combination with
other astrophysical probes) convincingly show the existence of non-baryonic
dark matter, the cosmic neutrino background, flatness of spatial geometry of
the universe, a deviation from a scale-invariant spectrum of initial scalar
fluctuations, and that the current universe is undergoing an accelerated
expansion. The WMAP observations provide the strongest ever support for
inflation; namely, the structures we see in the universe originate from quantum
fluctuations generated during inflation.
