Question about usage of the federated credentials.

[SilentImp]

Hi.
Am I correct, and all benefit of using federated credentials is getting information about which provider was used? For example, was it Facebook or Google? And then — sign in with API of this provider?
Also, is there a situation when we need to modify credentials? Just save them after the first login with Facebook or Google, and that's all?
Is there a full list of the providers that we need to pass to the FederatedCredential?
In the https://w3c.github.io/webappsec-credential-management/#provider-identification written that we should use an exact name, but:

1. why, if it's just a flag of login with the provider
2. which one? I don't know where to get these names.

Regards.