A VoIP phone also called an IP phone uses voice over IP technologies allowing telephone calls to be made over an IP network such as the Internet instead of the ordinary PSTN system.

VoIP phone can use different control protocols such as SIP or other proprietary protocols.

SIP Phone is a VoIP phone based on a Session Initiation Protocol that provides a SIP-based VoIP network. (see What is SIP? for more details)

VoIP phones can be a software-based - programs/applications named softphones or hardware devices also called desk-phones.