Hi @bryso,
Welcome to the Auth0 Community!
API calls requires an access token because they provide access a protected resource. Whereas ID tokens are used to provide information about the authenticated user.
An example of an API call is making a request with the Management API. To do so, you will need to get an access token for the Management API before you can call an endpoint in the API.
You could also have your own APIs, where you would need to get an access token to make those API calls.
I recommend reviewing the resources below for more information:
- Tokens
- ID Token and Access Token: What Is the Difference?
- Access token vs id token - #2 by john.gateley
Please let me know if you have any questions or need further clarification.
Thanks,
Rueben