Instead of opening wallets in shops and being confronted with a choice of whether to pay by cash or plastic card, they will wave a phone at the checkout.
Under the deal, Starbucks will use Square's service that lets customers who download the "Pay with Square" smartphone app and who enter their credit card information into it to pay simply by using their phone or by stating their name to employees at the cash register.
The key difference is that Square will allow the customers to pay with credit and debit cards on their phone, while Starbucks's current system only allows consumers to use their Starbucks debit card to pay.