a device which converts telephony traffic into IP for transmission over a data network

a network device that converts voice and fax calls, in real time, between the public switched telephone network (PSTN) and an IP network

a service that combines voice and data communication

A gateway is a point in a network where data gets changed from one format to another. In the case of a VoIP gateway it is where your internet phone call breaks out of the internet and onto the standard public telephone network. The voice data gets converted into a normal phone call for the rest of the journey until it reaches its destination.

A device that bridges the traditional circuit-switched PSTN and the packet-switched Internet.