“What is Google Voice?
Google Voice is a phone management system that is perfect for helping you stay organized.
Google Voice isn’t a phone service, but it lets you manage all of your phones. It works with mobile phones, desk phones, work phones, and VoIP lines. There’s nothing to download, upload, or install, and you don’t have to make or take calls using a computer.
Google Voice gives you one number for all your phones — a phone number that is tied to you, not to a device or a location. Use it to simplify the way you use phones, make using voicemail as easy as email, customize your callers’ experience, and more.
Google Voice lets you define which phones ring, based on who’s calling, and even let you listen to a voicemail before answering the call. We use smart technology to route your calls. So, if you’re already on a Google Voice call, we’ll recognize it and use call waiting to reach you on the phone you’re on.”
-via Google Voice