  In these lectures, we present the behavior of conventional $\bar{q}q$ mesons,
glueballs, and hybrids in the large-$N_{c}$ limit of QCD. To this end, we use
an approach based on rather simple NJL-like bound-state equations. The obtained
large-$N_{c}$ scaling laws are general and coincide with the known results. A
series of consequences, such as the narrowness of certain mesons and the
smallness of some interaction types, the behavior of chiral and dilaton models
at large-$N_{c},$ and the relation to the compositeness condition and the
standard derivation of large-$N_{c}$ results, are explained. The bound-state
formalism shows also that mesonic molecular and dynamically generated states do
not form in the large-$N_{c}$ limit. The same fate seems to apply also for
tetraquark states, but here further studies are needed. Next, following the
same approach, baryons are studied as bound states of a generalized diquark
($N_{c}-1$ antisymmetric object) and a quark. Similarities and differences with
regular mesons are discussed. All the standard scaling laws for baryons and
their interaction with mesons are correctly reproduced. The behavior of chiral
models involving baryons and describing chirally invariant mass generation is
investigated. Finally, properties of QCD in the medium at large-$N_{c}$ are
studied: the deconfinement phase transition is investigated along the
temperature and the chemical potential directions, respectively. Within the QCD
phase diagrams, the features of different models at large-$N_{c}$ are reviewed
and the location of the critical endpoint is discussed. In the end, the very
existence of nuclei and the implications of large-$N_{c}$ arguments for neutron
stars are outlined.
