The theory of electromagnetic beams is presented in a simple and physical way, with all necessary mathematics explained in the text. The topics covered are in free-space classical electrodynamics, but contact is made with quantum theory in proofs that causal beams of various kinds can be viewed as superpositions of photons. This follows from explicit expressions for the energy, momentum and angular momentum per unit length for each type of beam. The properties of beams in the focal region, of special experimental and theoretical interest, are discussed in detail. There are eight...