Google Voice is a service that aims primarily at unifying communication channels such that through one single, free phone number, several phones can ring. It works like most other phone numbers: give out your Google number for people to contact you. Upon an incoming call, you have several options to handle this communication.
At its core, Google Voice is not a VoIP service like Skype, but it does take advantage of VoIP technology over the internet in order to route some of its calls, to allow international calls at a cheap rate, to allow free local calls, and to offer the numerous features it is known for.
Google Voice gives you a phone number, known as a Google Voice number. With it, you can have incoming calls be forwarded to any phone of your choosing, be it your house phone, smartphone, or other phone.
