Google Wallet is the Google payment system which allows you to make payments in the safest way possible. You'll no longer need to carry your credit cards around with you, preventing them from being misplaced or stolen, and ensuring no money is lost from your accounts.
It is very easy to use Google Wallet, all you need to do is add your credit cards manually. If you've already linked any of them to your Google account, however, this tool will automatically add them for you, though certain details must be confirmed for security reasons. Once you've added all your credit cards you can switch between one and another to suit your needs at any given time.
Every time you visit a store and want to pay, just open Google Wallet and hold your mobile device near the payment system and the transaction will be carried out automatically. Remember that you can use it to pay in places where the point-of-sale terminal supports contactless payments, the same ones needed in order to pay by holding your card over them.