How laravel route:group wrapper works?

Laravel has really nice features of routing which made our life so comfortable. I am so curious about this Route::group() wrapper. How does it work and how does Roue class inside group wrapper get the information at group parameters. Is it maintain any global variable?

Route::group([
    'prefix' => 'audiobook',
    'middleware' => 'auth:api',
    'namespace' => 'Api\Audiobook'
], function () {
    Route::get('latest', 'AudioController@LatestAudioBook');
});

via Chebli Mohamed