  The light-front quantization of QCD provides an alternative to lattice gauge
theory for computing the mass spectrum, scattering amplitudes, and other
physical properties of hadrons directly in Minkowski space. Nonperturbative
light-front methods for solving gauge theory and obtaining light-front
wavefunctions, such as discretized light-front quantization, the transverse
lattice, and light-front resolvents are reviewed. The resulting light-front
wavefunctions give a frame-independent interpolation between hadrons and their
quark and gluon degrees of freedom, including an exact representation of
spacelike form factors, transition form factors such as $B \to \ell \bar \nu
\pi,$ and generalized parton distributions. In the case of hard inclusive
reactions, the effects of final-state interactions must be included in order to
interpret leading-twist diffractive contributions, nuclear shadowing, and
single-spin asymmetries. I also discuss how the AdS/CFT correspondence between
string theory and conformal gauge theory can be used to constrain the form and
power-law fall-off of the light-front wavefunctions. In the case of electroweak
theory, light-front quantization leads to a unitary and renormalizable theory
of massive gauge particles, automatically incorporating the Lorentz and 't
Hooft conditions as well as the Goldstone boson equivalence theorem.
Spontaneous symmetry breaking is represented by the appearance of zero modes of
the Higgs field, leaving the light-front vacuum equal to the perturbative
vacuum.
