In this seminar I will focus on cavity electrodynamics (CQED) as a quantum light-matter interface. When matter is placed in the mode of a high-finesse cavity, the interaction between the atoms and the field is enhanced since the light makes many round-trips inside the resonator. If the mode also has a small volume, quantum effects can become important as the field strength associated with a single photon can saturate an atomic transition, and a single atom can significantly affect cavity transmission. Thanks to these ideas, optical cavities can be used to efficiently transfer quantum states from single photons into atoms in a fully coherent and reversible manner. Since the dawn of quantum information science, a great deal of theoretical and experimental work has been done developing schemes to use CQED for quantum computing and quantum communication. The most promising direction seems to be quantum networking, where long-lived internal states of atoms are used as a quantum memory and cavities are used to transfer their state to photons, effective long-distance carriers of information.