Access tokens are used in token-based authentication to allow an application to access an API. The application receives an access token after a user successfully authenticates and authorizes access, then passes the access token as a credential when it calls the target API. The passed token informs the API that the bearer of the token has been authorized to access the API and perform specific actions specified by the Scope that was granted during authorization.
In addition, if you have chosen to allow users to log in through an Identity Provider (IdP), such as Facebook, the IdP will issue its own access token to allow your application to call the IDP's API. For example, if your user authenticates using Facebook, the access token issued by Facebook can be used to call the Facebook Graph API. These tokens are controlled by the IdP and can be issued in any format.
