The Pay API operation is used to transfer funds from a sender's PayPal account to one or more receivers' PayPal accounts. You can use the Pay API operation to make simple payments, chained payments, or parallel payments; these payments can be explicitly approved, preapproved, or implicitly approved. A chained payment is a payment from a sender that is indirectly split among multiple receivers. It is an extension of a typical payment from a sender to a receiver, in which a receiver, known as the primary receiver, passes part of the payment to other receivers, who are called secondary receivers.