SIP phones are communication devices that use the Session Initiation Protocol to make voice calls over the internet. Unlike traditional phones that rely on analog signals, SIP phones convert voice into digital data, allowing for clearer calls and additional features like video conferencing and instant messaging. They can be hardware-based, resembling regular phones, or software-based, functioning as applications on computers or smartphones. These phones connect to a VoIP (Voice over Internet Protocol) network, enabling users to make calls without traditional phone lines. SIP phones are popular in both business and personal settings due to their flexibility, cost-effectiveness, and ability to integrate with various communication systems.