An IP Telephone designed to work with an IP PBX. Modern SIP phones are also able to work without being constrained to a particular office or location. So we now can have on-premise phones and remote phones. Also, today’s mobile phones can run SIP software-based phones, allowing you to take your extension with you anywhere!
IP Phones are sometimes called VOIP telephones, SIP phones or soft phones. These are just different names for a device/software client that is designed to support the transmission of voice over the internet.