  Generalized parton distributions (GPDs) provide a link between form factors,
parton distributions and other observables. I discuss the connection between
GPDs and parton distributions as a function of the impact parameter. Since this
connection involves GPDs in the limit of vanishing skewedness parameter $\xi$,
i.e. when the off-forwardness is purely transverse, I also illustrate how to
relate $\xi\neq 0$ data to $\xi=0$ data, which is important for experimental
measurements of these observables.
