Stands for "Fiber Optic Service." FiOS is a data communications service provided by Verizon that uses fiber optic cables to transfer data. FiOS is called a "Fiber to the Premises," or FTTP service, since it brings fiber optic data transmission to residential homes as well as businesses. Since fiber optic technology sends data via pulses of light, it is the fastest method of transferring data.
While FiOS is currently used primarily for Internet access, it can also be used for digital cable and voice over IP (VoIP) services. For this reason, FiOS is considered to be a potential competitor to both cable and Internet Service Providers.