Voice over Internet Protocol (VoIP) is a purpose built software technology to support the transmission of voice over the Internet. The term VoIP is commonly used quite generically and is also sometimes called IP telephony, Internet telephony, broadband telephony or voice over broadband.

The primary VoIP value proposition is cost savings when compared to traditional telephone company services and plans. VoIP to VoIP phone calls are normally free, however VoIP calls connecting to public switched telephone networks (VoIP-to-PSTN), may carry a cost that is absorbed by the VoIP user. VoIP has evolved beyond just cost savings to include useful features and plans with provide additional advantages. VoIP services provided by broadband telephone companies usually include common features such as caller ID, voice mail and call forwarding that are considered “advanced” by the old guard telephone companies who often charge additional fees.

VoIP telephone usage is no different than the traditional legacy telephone operation from your phone company. Just pick up the phone, listen for the dial-tone and dial the destination telephone number. Most VoIP services do not require any extra numbers to dial and there are no special dialing routines necessary. It's simple.

VoIP telephone services shares the same Internet connection as your personal computer and both can be used at the same time.

Most VoIP phone to phone setups provide you with a phone adapter. You can also use your computer to make telephone calls simply by plugging a headset into the USB port and installing a simple software driver.

The below physical diagram shows a common telephone to telephone call path. This is the model most commonly used by providers such as Vonage and SunRocket.