In the world of Angular, interceptors have been used to pre-process and post-process the HTTP request before sending and after getting response from the server. Interceptors can be used in two different phases in a life cycle of an HTTP request to a server, which are:

1. Before making the request server: This happens before the call is made to server. It can be used change the request configuration of HTTP call. The most common use case for this is to add an Access Token to be sent to the server with each HTTP request so that it can be validated at server end.

1. After Getting the response from server: This happens once we get the response from the server. It can be used change the response before it is being passed to the code block from where HTTP call was made. The most common use case for this is to Handle Global Error Handling across the app.

Check below links
https://itnext.io/understanding-angular-interceptors-405b84d7ad69

https://blog.angularindepth.com/top-10-ways-to-use-interceptors-in-angular-db450f8a62d6