What token to use?

Your sample app on port 5555 shows Access token and ID token after the successful sign in. I understand Access token is OAuth2 token. Introspection of the token gives the required information for the application to give or reject an access to protected resources.
But what is ID token in this case? When should it be used but not the access token? How to introspect it’s content? How is it different from the Access token?

ID token is the identity token. It is a structure with the “claims” related to the identity. Usually the ID token is NOT used for authorizing the API calls.

Your hotel pass that opens your room is the access token (faceless, with the logo of the hotel but without your room number or your name written on it). It expires in 4 days. Your driver license is an ID [token] that contains the claim such as your first/last name etc. This pass does not allow you to enter your hotel room, the door won’t open. But you may need this ID to acquire your temporary hotel pass (access token).

ID token is usually a JWT, self-containing object, signed, that signature can be validated to confirm its origin.

Thank you very much for your answer. It is very helpful