  A remarkable feature of QCD is that the mass scale which controls color
confinement and hadron mass scales does not appear explicitly in the QCD
Lagrangian. However, de Alfaro, Fubini, and Furlan have shown that a mass scale
can appear in the equations of motion without affecting the conformal
invariance of the action if one adds a term to the Hamiltonian proportional to
the dilatation operator or the special conformal operator. Applying the same
procedure to the light-front Hamiltonian leads to a unique confinement
potential $\kappa^4 \zeta^2$ for mesons, where $\zeta$ is the LF radial
variable conjugate to the invariant mass. The same result, including spin
terms, is obtained using light-front holography, the duality between the front
form and AdS$_5,$ if one modifies the action by the dilaton $e^{\kappa^2 z^2}$
in the fifth dimension $z$. Generalizing this procedure using superconformal
algebra, leads to a unified Regge spectroscopy of meson, baryon, and
tetraquarks, including remarkable supersymmetric relations between the masses
of mesons and baryons of the same parity. One also predicts observables such as
hadron structure functions, transverse momentum distributions, and the
distribution amplitudes defined from the hadronic light-front wavefunctions.
The mass scale underlying confinement and hadron masses can be connected to the
mass parameter in the QCD running coupling by matching the nonperturbative
dynamics to the perturbative QCD regime. The result is an effective coupling
defined at all momenta and the determination of a momentum scale which sets the
interface between perturbative and nonperturbative hadron dynamics. I also
discuss evidence that the antishadowing of nuclear structure functions is
non-universal, and why shadowing and antishadowing phenomena may be
incompatible with sum rules for nuclear parton distribution functions.
