  AdS/QCD, the correspondence between theories in a dilaton-modified
five-dimensional anti-de Sitter space and confining field theories in physical
space-time, provides a remarkable semiclassical model for hadron physics.
Light-front holography allows hadronic amplitudes in the AdS fifth dimension to
be mapped to frame-independent light-front wavefunctions of hadrons in physical
space-time. The result is a single-variable light-front Schrodinger equation
which determines the eigenspectrum and the light-front wavefunctions of hadrons
for general spin and orbital angular momentum. The coordinate z in AdS space is
uniquely identified with a Lorentz-invariant coordinate zeta which measures the
separation of the constituents within a hadron at equal light-front time and
determines the off-shell dynamics of the bound state wavefunctions as a
function of the invariant mass of the constituents. The hadron eigenstates
generally have components with different orbital angular momentum; e.g., the
proton eigenstate in AdS/QCD with massless quarks has L=0 and L=1 light-front
Fock components with equal probability. Higher Fock states with extra
quark-anti quark pairs also arise. The soft-wall model also predicts the form
of the non-perturbative effective coupling and its beta-function. The AdS/QCD
model can be systematically improved by using its complete orthonormal
solutions to diagonalize the full QCD light-front Hamiltonian or by applying
the Lippmann-Schwinger method to systematically include QCD interaction terms.
Some novel features of QCD are discussed, including the consequences of
confinement for quark and gluon condensates. A method for computing the
hadronization of quark and gluon jets at the amplitude level is outlined.
