  Despite quantum chromodynamics (QCD) being established as the theory of the
strong interaction and its many successes since then, significant challenges in
our understanding of hadron physics remain. The lack of a full understanding
for how the observed hadrons arise from the quark and gluon degrees of freedom
which define QCD represents a real challenge in connecting the theory to
experiment. In particular, the rich spectrum of hadrons marks a significant gap
in our understanding, as no model can currently explain all observed hadrons
and QCD itself has only been used to study a small subset of the full spectrum.
The significant hurdle for using QCD directly is due to the non-perturbative
nature of the theory at low energies, requiring methods like lattice QCD. Here,
the spectrum of hadrons and how it relates to few-body dynamics is reviewed,
with a focus on state-of-the-art methods for their study through lattice QCD.
