  We sketch the basic ideas of the lattice regularization in Quantum Field
Theory, the corresponding Monte Carlo simulations, and applications to Quantum
Chromodynamics (QCD). This approach enables the numerical measurement of
observables at the non-perturbative level. We comment on selected results, with
a focus on hadron masses and the link to Chiral Perturbation Theory. At last we
address two outstanding issues: topological freezing and the sign problem.
