This lecture covers the principles of dielectric laser accelerators, focusing on the acceleration of charged particles by electromagnetic waves. Topics include the Lawson-Woodward Theorem, requirements on accelerating structures, rectangular and cylindrical waveguides, dielectric lined waveguides, and laser-driven accelerating structures. The lecture also discusses the design goals, first experiments at SLAC, flat structures, peak gradient as a function of laser field, and measurements of wake fields and energy gain in relativistic electrons.