The Moto 360 Gen 3 packs in support for Google Pay. This is a way to carry your credit and debit cards with you on the watch.
You can tap your watch to a reader at supported stores or vending machines and it will make the payment for you. Once you set it up, you can load these onto your watch for easy use.
You'll find support for most major credit cards and banks, and even many smaller banks and credit unions are adding support.