This means, you can change the content of all the handler functions you want, by creating new functions with the same name and overriding them in the conntroller files.
Combine with reading the contents of the route files to understand the tasks of the controller and its functions.
Controllers for the front-end are located in the directory "S-cart-folder/app/Http/Controllers". They are extended from the controllers in "S-cart-folder/vendor/s-cart/core/src/Front/Controllers".
Controllers for the admin are located in the directory "S-cart-folder/app/Admin/Controllers". They are extended from the controllers in "S-cart-folder/vendor/s-cart/core/src/Admin/Controllers".