How are custom classes created in Laravel?

Question

Laravel

For example, I need a separate class that I could access from different controllers.
This class should contain methods for loading and processing comments.

Answer 1

class A 
{
    ...
}

Answer 2

First phptherightway.ru
Then https://laravel.com/docs
And practice https://laracasts.com/series/laravel-5-from-scratch