A SIP trunk is a virtual connection between a company’s private branch exchange (PBX) system and a service provider’s network that enables the company to make and receive voice and video calls over the Internet Protocol using SIP. In other words, it is a VoIP connection that allows a business to communicate with the outside world using the Internet instead of traditional phone lines. A SIP trunk can replace traditional analog or digital phone lines, allowing companies to reduce costs and improve their communications capabilities. Such trunks also support a variety of advanced features, including unified communications, call routing, and call forwarding.