  Generalized parton distributions have been introduced in recent years as a
suitable theoretical tool to study the structure of the nucleon. Unifying the
concepts of parton distributions and hadronic form factors, they provide a
comprehensive framework for describing the quark and gluon structure of the
nucleon. In this review their formal properties and modeling are discussed,
summarizing the most recent developments in the phenomenological description of
these functions. The status of available data is also presented.
