A VoIP phone or IP phone uses voice over IP technologies for placing and transmitting telephone calls over an IP network, such as the Internet. This is in contrast to a standard phone which uses the traditional public switched telephone network (PSTN).
Digital IP-based telephone service uses control protocols such as the Session Initiation Protocol (SIP), Skinny Client Control Protocol (SCCP) or various other proprietary protocols.
A telecommunications company is a kind of electronic communications service provider, more precisely a telecommunications service provider (TSP), that provides telecommunications services such as telephony and data communications access. Many traditional solely telephone companies now function as internet service providers (ISPs), and the distinction between a telephone company and ISP has tended to disappear completely over time, as the current trend for supplier convergence in the industry develops. Additionally, with advances in technology development, other traditional separate industries such as cable television, Voice-over IP (VoIP), and satellite providers offer similar competing features as the telephone companies to both residential and businesses leading to further evolution of corporate identity have taken shape.
Due to the nature of capital expenditure involved in the past, most telecommunications companies were government-owned agencies or privately owned monopolies operated in most countries under close state regulation. But today there are many private players in most regions of the world, and even most of the government-owned companies have been opened up to competition in-line with World Trade Organization (WTO) policy agenda. Historically, these government agencies were often referred to, primarily in Europe, as PTTs (postal, telegraph and telephone services). Telecommunications companies are common carriers, and in the United States are also known as local exchange carriers. With the advent of mobile telephony, telecommunications companies now include wireless carriers, or mobile network operators and even satellite providers (Iridium).
Voice over Internet Protocol (VoIP), also known as IP telephony, is a set of technologies used primarily for voice communication sessions over Internet Protocol (IP) networks, such as the Internet. VoIP enables voice calls to be transmitted as data packets, facilitating various methods of voice communication, including traditional applications like Skype, Microsoft Teams, Google Voice, and VoIP phones. Regular telephones can also be used for VoIP by connecting them to the Internet via analog telephone adapters (ATAs), which convert traditional telephone signals into digital data packets that can be transmitted over IP networks.
The broader terms Internet telephony, broadband telephony, and broadband phone service specifically refer to the delivery of voice and other communication services, such as fax, SMS, and voice messaging, over the Internet, in contrast to the traditional public switched telephone network (PSTN), commonly known as plain old telephone service (POTS).