Waveguides are conduits used to guide electromagnetic waves along a path. These paths can be hollow metal tubes, dielectric filled open conduits or a combination of both. There are several synonyms used for the term waveguides. These include transmission lines, resonant cavities, guided wave paths, and fiber optic lines. The term resonant cavities refer to structures that contain a wavelength of the electromagnetic wave. Guided wave paths are channels that direct the wave through specific angles and shapes. Lastly, fiber optic lines are similar to waveguides, but they use light to carry signals rather than electromagnetic waves. In summary, these synonyms all refer to the technology used to transfer electromagnetic energy from one place to another using a specialized channel.