VoIP which stands for Voice over Internet Protocol allows you to make telephone calls using a computer. The computer uses a data network like the Internet to transmit the information and then converts your voice signal when you speak into your computer microphone or VoIP phone into a digital signal.
This signal travels across the internet and is converted back to a voice signal so that the person can hear your voice either on their phone or on their computer speakers.
In order to use VoIP you will need to install software onto your computer, for example Skype, and for the best results use a headset with built-in microphone. You can also buy an adaptor for your regular home phone or buy a dedicated VoIP telephone, which looks just like a regular phone.