Web-hooks are a notification system that could be compared to a callback. Basically, pagure will make a HTTP POST request to one or more third party server/application with information about what is or just happened.
To set-up a web-hook, simply go to the settings page of your project and enter the URL to the server that will receive the notifications.
In the settings page is also present a web-hook key which is used by the server to sign the message sent and which you can use to ensure the notifications received are coming from the right source.
Each POST request made contains two specific headers:
X-Pagure-Topic X-Pagure-Signature
X-Pagure-Topic is a global header giving a clue about the type of action
that just occured. For example issue.edit.
X-Pagure-Signature contains the signature of the message allowing to
check that the message comes from pagure.