Telephony is a term that refers to the technology that allows people to make long-distance calls. It comes from the word 'telephone', which in turn is derived from the two Greek words 'tele', meaning far, and 'telephone', meaning to speak, hence the idea of speaking at a distance. The scope of the term has broadened with the advent of new communication technologies. In the broadest sense, the terms include telephone communication, internet calling, mobile communication, faxing, voicemail and even videoconferencing. Ultimately, it is difficult to draw a clear line between what is telephony and what is not.

The original idea that telephony is returning to is POTS (plain old telephone service), technically called PSTN (public switched telephone network). This system is fiercely challenged by and largely yields to Voice over IP (VoIP) technology, also called IP telephony and Internet telephony.

These two terms are used interchangeably in most cases, but technically they are not exactly the same. The three terms that personify each other are Voice over IP, IP Telephony and Internet Telephony. They all refer to the channeling of voice calls and voice data over IP networks, namely LANs and the Internet. In this way, existing facilities and resources that are already used for data transmission are utilized, thus eliminating the cost of expensive line assignment as is the case with the PSTN. The main advantage that VoIP offers users is significant cost savings. Calls are also often free.

This, together with the many advantages that VoIP brings, has made the latter an important technological element that has become popular worldwide and has claimed the lion's share of the telephony market. The term Computer Telephony originated with the advent of softphones, applications that are installed on a computer, mimic a telephone and use VoIP services on the Internet. Computer telephony has become very popular because most people use it for free.