What is VoIP?

CNET has a useful guide to VoiP and other Internet telephone technology and products.  (CNET: Internet Phones)

VoIP - Voice over Internet Protocol. This is the technology used to transmit voice conversations as data over net using the Internet Protocol.

There are so many products available these days that uses VoIP thechnology 

VoIP or Voice over Internet Protocol, is nothing but communication with the help of internet. For this, all you need is an internet connection, a phone that supports VoIP and a PC. First of all you need a service provider, who would give you internet connectivity. With the help of internet, you can make calls to anywhere in the world. These calls are known as Web Calls. You can make both voice calls and video calls.

VoIP Stands for Voice over Internet Protocol. You can read more on VoIP Here: How VoIP Works

In terms of using VoIP to call people, it basically uses an internet connection instead of the normal analogue system. This is cheaper and costs pretty much the same no matter where in the world you are calling.

A good comparison I read was comparing it to fax and email. A normal telephone is like faxing a letter, and a VoIP enabled phone is like emailing the letter.

VOIP uses the internet as a backbone to carry digital telephone calls.

VoIP or voice over internet protocol is a phone networks uses internet to make calls. VoIP phones have more features that traditional phones but you must have voip service provider to provide your number and connection. Try RingCentral and experience their services.