Postback is a message or value that is passed to ChatBot when a user clicks a button.
Let’s say you use a Gallery response with multiple cards. Each card presents a different product, but all have the same button title, View. In such a case, you can add a specific postback message or value to each card to distinguish which button was clicked.
Postback is treated as a user query and can be saved by the entity following it. For example, you can add a subsequent interaction with the Any validation to save the ChatBot pricing answer as an attribute.