  We outline in detail the properties of generalized parton distributions
(GPDs), which contain new information on the structure of the nucleon and which
enter the description of hard exclusive reactions. We highlight the physics
content of the GPDs and discuss the quark GPDs in the large $N_c$ limit and
within the context of the chiral quark-soliton model. Guided by this physics,
we then present a general parametrization for these GPDs. Subsequently we
discuss how these GPDs enter in a wide variety of hard electroproduction
processes and how they can be accessed from them. We consider in detail deeply
virtual Compton scattering and the hard electroproduction of mesons. We
identify a list of key observables which are sensitive to the various nucleon
structure aspects contained in the GPDs and which can be addressed by present
and future experiments.
