To allow customers to login using Facebook, Google, and other social sign-on providers, the identity architect should configure an authentication provider and a registration handler for each social sign-on provider. Authentication providersare configurations that enable users to authenticate with an external identity provider and access Salesforce resources. OpenID Connect is a protocol that allows users to sign in with an external identity provider, such as Facebook or Google, and access Salesforce resources. To enable this, the identity architect needs to configure an OpenID Connect Authentication Provider in Salesforce and link it to aconnected app. A registration handler is a class that implements the Auth.RegistrationHandler interface and defines how to create or update users in Salesforce based on the information from the external identity provider. The registration handler can also be used to link the user’s social identity with their Salesforce identity and prevent duplicate accounts.References: OpenID Connect Authentication Providers, Social Sign-On with OpenID Connect, Create a Custom Registration Handler