  We give an overview of the theory for generalized parton distributions.
Topics covered are their general properties and physical interpretation, the
possibility to explore the three-dimensional structure of hadrons at parton
level, their potential to unravel the spin structure of the nucleon, their role
in small-x physics, and efforts to model their dynamics. We review our
understanding of the reactions where generalized parton distributions occur, to
leading power accuracy and beyond, and present strategies for phenomenological
analysis. We emphasize the close connection between generalized parton
distributions and generalized distribution amplitudes, whose properties and
physics we also present. We finally discuss the use of these quantities for
describing soft contributions to exclusive processes at large energy and
momentum transfer.
