  We present a pedagogical overview of flux compactifications in string theory,
from the basic ideas to the most recent developments. We concentrate on closed
string fluxes in type II theories. We start by reviewing the supersymmetric
flux configurations with maximally symmetric four-dimensional spaces. We then
discuss the no-go theorems (and their evasion) for compactifications with
fluxes. We analyze the resulting four-dimensional effective theories, as well
as some of its perturbative and non-perturbative corrections, focusing on
moduli stabilization. Finally, we briefly review statistical studies of flux
backgrounds.
