  Light-Front Quantization provides a physical, frame-independent formalism for
hadron dynamics and structure. Observables such as structure functions,
transverse momentum distributions, and distribution amplitudes are defined from
the hadronic light-front wavefunctions. One obtains new insights into the
hadronic spectrum, light-front wavefunctions, and the functional form of the
QCD running coupling in the nonperturbative domain using light-front holography
-- the duality between the front form and AdS$_5$, the space of isometries of
the conformal group. In addition, superconformal algebra leads to remarkable
supersymmetric relations between mesons and baryons of the same parity. The
mass scale $\kappa$ underlying confinement and hadron masses can be connected
to the parameter $\Lambda_{\overline {MS}}$ in the QCD running coupling by
matching the nonperturbative dynamics, as described by the effective conformal
theory mapped to the light-front and its embedding in AdS space, to the
perturbative QCD regime. The result is an effective coupling defined at all
momenta. This matching of the high and low momentum transfer regimes determines
a scale $Q_0$ which sets the interface between perturbative and nonperturbative
hadron dynamics. The use of $Q_0$ to resolve the factorization scale
uncertainty for structure functions and distribution amplitudes, in combination
with the principle of maximal conformality (PMC) for setting the
renormalization scales, can greatly improve the precision of perturbative QCD
predictions for collider phenomenology. The absence of vacuum excitations of
the front-form vacuum has important consequences for the cosmological constant.
I also discuss evidence that the antishadowing of nuclear structure functions
is flavor dependent, and why shadowing and antishadowing phenomena may be
incompatible with sum rules for nuclear parton distribution functions.
