VoIP also called Internet telephony, is a technologies that uses your internet connection to route your phone calls. This technology has matured a lot in the last few years. Nowadays this works just like classics phones and millions of people in the US use it every day.
You will find absolutely no difference with a regular phone line. Although some VoIP providers claim, their VoIP offer, works over dialup, we definitely recommend broadband for a better experience.

Concretely you will receive a little modem that you plug to your network and then plug your phone to the VoIP modem. This works very well if you have one of those phone system that has a central phone connected with a wire, to which you can add additional wireless phones. With this set-up you can have the main phone connected to the modem (with a wire) and wireless phone throughout the home (bedrooms, basements ..etc...). If you are used to having just one phone in your home/office you probably do not need those wireless phone systems.

911: VoIP provider are required by law to offer a way to link your VoIP line to a physical address. This way a 911 call can be traced back to a physical address. Make sure you communicate a "911" physical address to the VoIP provider. If not, the 911 service,  will never be able to link your call back to your home/office.

If you internet connection is flaky, VoIP might not be for you. Since VoIP uses your internet connection to route phone calls, it will not work when your internet connection is "down".

Dozen of providers offer VoIP. Usually your cable TV company and your local phone company will offer VoIP. Here are some of the main players.

SunRocket (Excellent Price, Excellent International Plan)

Packet8 (one of the oldest but also a little more expensive)

ViaTalk offers some of the best prices (and offer a limited time special of 1 free year):