Entangled states of light

These notes are more or less a faithful representation of my talk at the Workshop on ``Quantum Coding and Quantum Computing'' held at the University of Virginia. As such it is an introduction for non-physicists to the topics of the quantum theory of light and entangled states of light. In particular, I discuss the photon concept and what is really entangled in an entangled state of light (it is not the photons). Moreover, I discuss an example that highlights the peculiar behavior of entanglement in an infinite-dimensional Hilbert space.