According to paypal docs: https://developer.paypal.com/webapps/developer/docs/classic/adaptive-payments/gs_AdaptivePayments/
A parallel payment is a payment from a sender that is split directly among 2-6 receivers.
Technically, a parallel payment is a set of multiple payments made in a single Pay request.
Parallel payments are useful in cases when a buyer intends to make a single payment for items
from multiple sellers. Examples include the following scenarios:
a single payment for multiple items from different merchants, such as a combination of
items in your inventory and items that partners drop ship for you.
purchases of items related to an event, such as a trip that requires airfare, car rental, and a hotel booking.
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.