Every person uses some kind of communication. Everyone has own privacy requirements, preferences and cost limits. Telephone systems cannot offer customizable service but new types of communication can change that. Whit things line email and Instant Messaging we can do things like sorting incoming messages, set different filters and change our online status to busy or disable incoming messages from some users. We cannot expect the same features from our telephone system but it would be amazing if instead of getting a busy signal we could just see if the person is available instantly just like we do when chatting through Internet.
These features are offered by the Voice over Internet Protocol which extends the capabilities of the ordinary phone calls and that is because of its flexibility and the fact that it can be configured to do things that cannot be done by a ordinary PSTN telephone. Maybe nowadays almost everyone knows that VoIP can offer making very call Nepal no matter your location and without a wireless data plan. This one looks like the service provided by Google called Google Voice but it is not exact the same. The difference is that the VoIP service is hosted on servers of Google.