Google Voice

Google Voice is a free service that provides a free U.S. phone number, chosen by the user from available numbers in selected area codes for a user account.

The main purpose of Google Voice is to provide you a single phone number, entirely free, that you hand out to everyone, so when a call is placed or text sent, it forwards to all your numbers. That way, if an important call comes in, it can ring your cell, your home number, your office number, and others all at once—pick up the one you want. (This is less and less an issue in the one-phone-per-person mobile world.)

However, the Google Voice apps also feature dialers so you can call or text out with your Google Voice number—the recipient will see it and if they return the call, you'll get it at the preset numbers (or get a voicemail with full text transcription). 

Remember, if you have a Google account, you've probably got a Google Voice account already.

Google Voice

Users must have an existing U.S. telephone number to activate a Google Voice phone number. 

The user then must configure this additional phone number to ring on one of their existing cell or land based phone lines. 

This will make all Google Voice calls forward and ring on those devices. 

Google Voice services include voicemail, free text messaging, call history, conference calling, call screening, blocking of unwanted calls, and voice transcription to text of voicemail messages.