A fiber optic cable is a cable designed to carry optical light as opposed to carrying electrical current.  Optical fiber is essentially an extruded piece of glass, which is known as the core of the cable and the part where the light is traveling. A protective coating, known as cladding surrounds the core.  The two together form a fiber optic cable and create the condition where the light within the cable can experience total internal reflection. This means the light does not escape or leak out of the cable as it travels down the cable but rather be contained within the cable. This is a desired property for good fiber optic cables. The cladding is then coated with a polymer material to help protect the cladding and core, but this coating does not determine the behavior of the internal reflective properties. Some cables, due to the way they are manufactured, will experience some loss of light.

A fiber optic cable essentially is an optical waveguide, as light is simply guided down the cable by a series of internal reflections, causing it to propagate down the length of the cable.

Fiber optic cables can have multiple different light sources traveling down the same piece of cable, which are all operating on different optical wavelengths (colors). This is called wavelength division multiplexing. It is also possible to have multi-core cables, which are optically separated but all contained within a single sheathed cable - similar to a multi-conductor cable.