  We explore the physics of the parton-hadron duality in the nucleon structure
functions appearing in lepton-nucleon scattering. We stress that the duality
allows one to extract the higher-twist matrix elements from data in the
resonance region, and learn about the properties of resonances if these matrix
elements are known. As an example, we construct the moments of $F_2(x, Q^2)$
for the low and medium $Q^2$ region, and from which we study the interplay
between higher twists and the resonance contributions.
