VoIP is a communications technology that enables you to make phone calls using your broadband connection instead of landline service. VoIP stands for Voice over Internet Protocol, which is an open standard for establishing calls through the Internet. Some may also refer to VoIP as Voice over IP.
The portable or fixed handset uses the internet to transmit your speech like a physical landline would. The only difference is that the underlying technology isn’t a landline but the Internet. VoIP handsets can be powered by your network switches that are capable of PoE. (Power over Ethernet)