Fiber optics is a science and engineering discipline specializing in the use of glass or plastic fibers to transmit light. A fiber optic cable consists of a bundle of these fibers, each capable of transmitting information in the form of light pulses.
For communications, optical fiber has significant advantages over copper wire. Both methods are electromagnetic waveguides. In the case of copper wires, the electromagnetic waves are guided between two conductors -- a pair of wires; whereas in an optical fiber, the waves are light, guided by the internal structure of the glass fiber. Optical fiber is immune to electromagnetic interference; leakage of signal from one fiber to another is much less of a problem than cross-talk between electrical waveguides; optical fiber can be made to have less attenuation than copper. These advantages allow the pulses of light to be switched on and off much more rapidly than the pulses of electricity in wires, so that more information can be sent per second. The speed the light propagates is not significantly different than that of the electrical pulses in copper.