Applications need the following input to take a payment:
The amount to charge.
The payment recipient. The payment goes to the account identified by the Authorization header in the API request.
The payment source. The source can be a payment token or card on file.
You can generate a payment token using the Web Payments SDK and the In-App Payments SDK. For working code examples, see Square Connect API Examples.
A card on file is a credit card, debit card, or gift card that is associated with a customer. You can create a customer and add a card on file using Square APIs, the Square Seller Dashboard, or the Square Point of Sale application.
For more information, see the following guides: