How VoIP / Internet Voice Works
VoIP converts the voice signal from your telephone into a digital signal that travels over the Internet. If you are calling a regular phone number, the signal is then converted back at the other end. Internet Voice can allow you to make a call directly from a computer. If you make a call using a phone with an adaptor, you'll be able to dial just as you always have, and the service provider may also provide a dial tone. If your service assigns you a regular phone number, then a person can call you from his or her regular phone without using special equipment.
What Kind of Equipment Do I Need?
A broadband Internet connection is required to make VoIP calls. Some services allow you to use a regular telephone, as long as you connect it to an adaptor. Some companies allow you to make calls from a computer or a VoIP phone that doesn't require an additional adapter. If you are calling a regular telephone number, the person you are calling does not need any special equipment, just a phone.
If I have VoIP Service, Whom Can I Call?
Depending upon your service, you might be limited only to other subscribers to the service, or you may be able to call any phone number, anywhere in the world. The call can be made to a local number, a mobile phone, a long distance, or an international number.
What Are Some Advantages of VoIP?
Because VoIP is digital, it may offer features and services that are not available with a traditional phone. If you have a broadband Internet connection, you need not maintain and pay the additional cost for a line just to make telephone calls.
Does My Computer Have to be Turned On?
Not if you are making calls with a phone and adaptor or special VoIP phone, but your broadband Internet connection needs to be active. You can also use your computer while talking on the phone.
Is There a Difference Between Making a Local Call and a Long Distance Call?
Some VoIP providers offer their service for free, normally only for calls to other subscribers to the service. Some VoIP providers charge for a long distance call to a number outside your calling area, similar to existing, traditional wireline telephone service. Other VoIP providers permit you to call anywhere at a flat rate for a fixed number of minutes.
Your VoIP provider may permit you to select an area code different from the area in which you live. This means that if your provider charges for long distance, then charges could be based on whether you call within your area code rather than geographic area. It also means that people who call you may incur long distance charges depending on their area code and service.
Can I Take My Phone Adapter With me When I Travel?
You may be able to use your VoIP service wherever you travel as long as you have a broadband Internet connection available. In that case it would work the same as in your home.
How Do I Know If I have a VoIP Phone Call?
The phone will ring like any other call.

Article from Fcc.gov