  Reheating is an important part of inflationary cosmology. It describes the
production of Standard Matter particles after the phase of accelerated
expansion. We give a review of the reheating process, focusing on an in-depth
discussion of the preheating stage which is characterized by exponential
particle production due to a parametric resonance or tachyonic instability. We
give a brief overview of the thermalization process after preheating and end
with a survey of some applications to supersymmetric theories and to other
issues in cosmology such as baryogenesis, dark matter and metric preheating.
