Laravel 5.5 - laravel/socialite scopes and redirect

Can somebody explain to me what are scopes in laravel/socialite and how can I define multiple redirect from services.php

I need one for sign up with facebook, and another for login with facebook

config/services.php

'facebook' => [
        'client_id' => '***************',
        'client_secret' => '****************',
        'redirectForSignUp' => 'http://localhost:8000/register/facebook/callback',
        'redirectForLogin' => 'http://localhost:8000/login/facebook/callback',
 ],

via Chebli Mohamed