Here are a few scenarios in which you would use webhooks:
If you want to have an internal points system for your users, webhooks let you add credits to users in your database every time a referral happens.
Every time a new participant joins your referral campaign, webhooks lets you save their unique referral link (and other information) into your database.
Go to the Options step in the Campaign Editor.
In the Automate rewards fulfillment section, select the Webhooks tab. Then enter your webhook endpoint URL.
Publish/save your changes.
View Examples of implementing webhooks, or view what the request payloads for webhook events look like: