Laravel built in Authentication

In a Laravel built in authentication, among the many available classes and interfaces, I have narrowed it down to Illuminate\Support\Facades\Auth and Illuminate\Auth\SessionGuardas am trying to figure out how the authentication works, can anyone please explain to me the principle or just how these two correlates such that am able to call Auth::check() or any of the related functions which are implemented by Illuminate\Auth\SessionGuard but not with Illuminate\Support\Facades\Auth. Thanks in advance.

P.S. Am trying to build my own custom authentication in laravel and i just want to understand this one.

via Chebli Mohamed