Generalized parton distributions for the deep QCD structure of the nucleon and its transitions

We introduce the generalized parton distributions (GPDs) of the nucleon and the transition GPDs, and summarize the physical meanings as well as important properties implied directly and indirectly from their QCD definitions. Hard nucleon scattering/transition processes to probe those GPDs relevant to ongoing and future experiments are explained and some illustrative examples are presented, demonstrating what deep structure of the nucleon, and its transitions to other baryons, are about to be revealed through theoretical and experimental efforts toward those processes. We also briefly mention a recent topic on the gravitational form factors parameterizing the nucleon matrix element of the QCD energy-momentum tensor, and their relations to the GPDs, such that the measurements of the GPDs allow the determination of the behaviors of gravitational form factors.