add auth guard laravel code example

Example 1: laravel check auth

use Illuminate\Support\Facades\Auth;

if (Auth::check()) {
    // The user is logged in...
}

Example 2: laravel guard

They arere the definition of how the system should store and retrieve 
]information about your users.

You can find the configuration in your config/auth.php

https://stackoverflow.com/questions/34896130/laravel-what-is-a-guard
https://mattstauffer.com/blog/multiple-authentication-guard-drivers-including-api-in-laravel-5-2/