Buy Buttons "are the ability to do one click payments" starting at one location/app but typically fulfilled/completed behind the scenes at a different location.
We've blogged about what's driving their rising popularity in the past. Here's a good article on ReadWrite about buy buttons and Pinterest with some comments from Spreedly.
The new callbacks functionality means that Spreedly customers can receive automated feedback and drive workflows based on the updated statuses of individual cards.
In this edition of Payments Dialog, Luke Evans and Peter Mollins discuss PSD2, SCA, and 3DS2 -- and what these regulations mean in the payments space.