Lattice Simulations and Effective Theories

I present a brief introduction to the lattice formulation of quantum field theory, and discuss the use of lattice simulations for studies in particle physics phenomenology. The computation of $f_B$, the decay constant of the $B$-meson, is used as a case study. I also explain the appearance and cancellation of ``renormalons’’ in the evaluation of power corrections (higher-twist corrections) in hard scattering and decay processes.