  A natural calculus for describing the bound-state structure of relativistic
composite systems in quantum field theory is the light-front Fock expansion
which encodes the properties of a hadrons in terms of a set of
frame-independent n-particle wavefunctions. Light-front quantization in the
doubly-transverse light-cone gauge has a number of remarkable advantages,
including explicit unitarity, a physical Fock expansion, the absence of ghost
degrees of freedom, and the decoupling properties needed to prove factorization
theorems in high momentum transfer inclusive and exclusive reactions. A number
of applications are discussed in these lectures, including semileptonic B-meson
decays, two-photon exclusive reactions, diffractive dissociation into jets, and
deeply virtual Compton scattering. The relation of the intrinsic sea to the
light-front wavefunctions is discussed. Light-front quantization can also be
used in the Hamiltonian form to construct an event generator for high energy
physics reactions at the amplitude level. The light-cone partition function,
summed over exponentially-weighted light-cone energies, has simple boost
properties which may be useful for studies in heavy ion collisions. I also
review recent work which shows that the structure functions measured in deep
inelastic lepton scattering are affected by final-state rescattering, thus
modifying their connection to light-front probability distributions. In
particular, the shadowing of nuclear structure functions is due to destructive
interference effects from leading-twist diffraction of the virtual photon,
physics not included in the nuclear light-cone wavefunctions.
