VoIP has many advantages like low cost, full mobility (you can call from your account from anywhere), has much extra functionality (like simultaneous video and data transmission), etc...
The internet has been a revolution greater than most other because it has ushered in an era of convergence wherein the computer has been made into some omnipotent enabler. Far from being merely a number cruncher, a computer is today a communication device and an entertainment medium. The internet has helped computer breach into the domain of telephony as well. VoIP (Voice over IP) is a novel technology that allows interpersonal voice communication at a fraction of the cost of subscriber telephony.
VoIP translates into Voice over Internet Protocol. It is a technology wherein voice in the form of data packets, are transferred on an IP network between two terminals with distinct IPs. The medium of transfer might be anything depending upon the mode of internet access (telephone lines, cable, satellite internet, power lines, etc), but data is packet-switched, rather than circuit-switched as in normal telephonic conversion. This results in optimum usage of network bandwidth, reduces latency and increases robustness of communication.
Significantly, internet is not necessary to VoIP – any network on IP domains can use VoIP for voice communication. It has many advantages like low cost, full mobility (you can call from your account from anywhere), has much extra functionality (like simultaneous video and data transmission), etc. It suffers from some drawbacks as well, including implementation challenges, higher learning curve for usage, reliability and security issues, etc. However, as policy and technology evolves, many of these issues would be settled. For now, VoIP is a wonderful concept that brings the power of voice communication to every network.