Yes. With an Internet phone, we can call anyone in the world that has a phone — extremely cheaply or even free.
The basic procedure is simple. See figure. Plug your current phone into a gateway box (a phone adapter and router) that the Internet phone company provides. Plug the gateway box into your broadband cable, satellite, or DSL modem to connect to the Internet. Pick up the phone, hear a dial tone, press the phone number into the phone’s keypad, let it ring, and then talk when the other person comes on the “line.” It seems like a normal phone call.
Sometimes, the connection is outstandingly clear with beautiful high fidelity — much better than we can ever get on a regular phone. Other times, when the Internet is crowded, we endure annoying lags in our conversation — something like the “buffering” lags when trying to watch video over the Internet.
Link: USA Today