VoIP is a broad term which refers to any call made over the internet rather than over a standard phone line. VoIP depends on IP (data connectivity) to transmit voice packets. SIP is a protocol used to initiate, maintain, and terminate voice communication sessions in VoIP applications. SIP protocols support the signalling and management of voice, video, and electronic messaging applications. SIP (Session initiation protocol) is used in VoIP (Voice over IP) technology.