Open the Google Play Store app or go to play.google.com/redeem, enter your gift card code, and select Redeem. The credit will be added to your account instantly.

The balance is added to your Google Play account and is available immediately.

You can use it to buy apps, games, movies, TV shows, books, music, and in-app purchases on Google Play.

Yes. Any remaining balance stays in your account and can be used for future purchases.