Add-ons are plugins associated with a client in Auth0. Usually, they are third-party APIs used by the client(s) that Auth0 generates Access Tokens for (for example, Salesforce, Azure Service Bus, Azure Mobile Services, SAP and more).
To view all the available add-ons for a client navigate to Dashboard > Clients > Addons.
Some typical scenarios for using add-ons include:
Accessing External APIs: Using the Delegation endpoint, you can exchange a Client's Access Token for a third-party service's (such as Salesforce or Amazon) Access Token.
Integrating with Applications Using SAML2/WS-Federation: Add-ons allow you to integrate with any custom or SSO integration that does not currently enjoy built-in Auth0 support, since they allow you to configure every aspect of the SAML2/WS-Federation integration.