SIP Phones are the same thing as VoIP Phones or soft phones. These are telephones that allow phone calls to be made using VoIP (voice over internet protocol) technology.
There are two types of SIP Phones. The first type is the hardware SIP phone, which resembles the common telephone but can receive and make calls using the internet instead of the traditional PSTN system.
SIP Phones can also be software-based. These allow any computer to be used as a telephone by means of a headset with a microphone and/or a sound card. A broadband connection and connection to a VOIP provider or a SIP server are also required.