  We underline the general features of the constituent quark model and its
success in the description of the spectrum and transitions of hadrons made up
of light or heavy quarks, briefly compared to first principles of QCD. To show
the present usefulness of the techniques and intuitive insight of the model we
present a semirelativistic quark model of meson form factors that exhibits
Isgur-Wise scaling and corrections to it. As examples of applications, we
consider semileptonic form factors and non-leptonic decays of heavy flavor
mesons. We address the issue of the violation of factorization, and show how
the quark model can give hints on the problem.

High Energy Physics - Phenomenology