Is also know as web callback or HTTP push API. It's a way for an app to provide other applications with real-time information or data.
The data can also be referred to as webhook or callback data.
The HTTP URL reserved to receive the data from another application(Dusupay) is called a webhook or callback URL
Therefore webhook and callback can be used inter-changeably
With reference to the webhook definition or understanding above, the webhook-hash is an extra piece of information that we include in the data sent to the webhook URL.
If you set your webhook-hash value under your merchant account API settings to say "XYZ", we will include a header webhook-hash with value "XYZ" Header: "webhook-hash: XYZ" This means that before your application where the webhook URL targets, receives data from Dusupay, it should first verify that the header "webhook-hash" contains the expected value "XYZ" known between Dusupay and the application receiving the information sent to the webhook URL as an extra level of security