Providers are upstream login services that you can configure within Identity Server. When a provider is configured, you can make it available to your client applications for login purposes.
Out of the box we provide the Windows Active Directory provider, preconfigured. With this available, your users can log in to your client applications using Windows Integrated Authentication.
You can optionally setup more providers as required, and choose which ones are available to particular client applications.
Currently we support setting up ADFS servers, however in the future we will provide support for Azure AD, Google, Facebook and many more.