"Interfaces to TAPI/SIP" refers to the integration of telephony applications with the Telephony Application Programming Interfaces (TAPI) or the Session Initiation Protocol (SIP). TAPI is a Microsoft standard for communication between PCs and telephone systems, while SIP is a widely used protocol for setting up, controlling, and terminating communication sessions over the Internet. Integrating these interfaces allows the software to initiate, receive, and control phone calls directly from a computer.