VoIP (Voice over IP, IP telephony) is a technology that lets subscribers to the VoIP service make telephone calls using a computer network that supports IP (Internet Protocol).
This means that anyone with a broadband Internet connection can replace their existing telephone connection with VoIP.
Some VoIP services only allow telephone calls to people using the same service, others allow calls to any number.
Some VoIP services work just through the computer, others require a special VoIP telephone or the fitting of a VoIP adapter to a conventional telephone.