The epoch of reionization probes the state of our universe when the very
first stars formed and ionized the hydrogen atoms in the surrounding medium.
Since the epoch has not yet been probed observationally, it is often called the
"final frontier" of observational cosmology. This final frontier is attracting
a lot of attention because of the availability of a large number of telescopes
in a wide variety of wavebands. This review article summarizes some of the
concepts required to understand the interesting physics of reionization and how
to analyze the high-redshift universe using related observations.
Comment: Review article published in a special issue of General Relativity and
Gravitation in memory of Professor T. Padmanabhan
Subject: Astrophysics - Cosmology and Nongalactic Astrophysics