Download the app and answer basic questions about yourself then Google will send you surveys around once a week, although it may be more or less frequent. You'll get a notification on your phone when a short and relevant survey is ready for you, and can receive up to $1.00 in Play credits for completing it.
Google's reward money can be used to buy real apps, ebooks, music, or whatever else you want to spend Play Store credit. That's money that didn't have to come out of your bank account, credit card, PayPal, or some other source of digital currency considered more valuable.
The app was available in the USA but has recently been made available for users in Denmark, Norway, and Sweden.
Click here to download Google Opinion Rewards from Google Play