Inline Hooks are outbound calls from Okta to your own custom code, triggered at specific points in Okta process flows. They allow you to integrate custom functionality into those flows.
You implement your custom code as a web service with an Internet-accessible endpoint. It's your responsibility to arrange hosting of your code on a system external to Okta. Okta defines the REST API contract for the requests it sends to your custom code, as well as for the responses your custom code can send back.
The outbound call from Okta is called a hook. Your code, which receives the call, is referred to as your external service.
Inline hooks use synchronous calls, which means that the Okta process that triggered the hook is paused until a response from your external service is received.
Learn more about Inline Hooks.