Voice over Internet Protocol is a technology that allows voice to be send over internet using a broadband internet connection and subscribing to a VoIP provider allows a person from call over the internet.

First, Voice is converted by a device from an anolog signal to a digital signal.
It is then sent over the internet where it will be converted back to an analog signal for the remainging distance over a traditional circuit switch (PSTN).

You will need a broadband Internet connection such as DSL or Cable or others(Wireless,..etc.).
Generally depending on variables such as the codec in use, a connection should have ar least l00 Kbps on both the upload and download.

Yes, you can work on the computer while on the VoIP phone. They should not conflict with each other.

There are several advantages to VoIP over a traditional phone service, such as,price, portability, and extra features. many VoIP providers allow unlimted calls through out the US and Canada at one low monthly Fee. the regulation of VoIP is less than traditional phone service making the cost cheaper.

Usually better, but the quality can depend on many factors like bandwith, Internet connections over the routed call, and the codec being used by the provider.