SIP is the technology used to carry voice calls over a data network. A SIP Trunk is a virtual line based on Voice over IP technology (VoIP) that uses your internet connection to manage incoming and outgoing calls when connected to a local phone system (PBX). These phone lines are “software” based, and not delivered physically but through your internet connection.
In short, SIP Trunking is a great option for those organizations that want to take advantage of VoIP Telephony like unlimited calling and lower costs but are not ready to move their entire phone system to the cloud. Instead, they replace their current traditional lines for VoIP lines and move one-step forward towards the cloud.