Mounting a query with laravel

I'm studying the laravel structure from this ready-made example = > bestmomo .

In the project there is the userRepository repository with the following structure:

<?php

namespace App\Repositories;

use App\Models\User;

class UserRepository
{
    /**
     * Get users collection paginate.
     *
     * @param  int  $nbrPages
     * @param  array  $parameters
     * @return \Illuminate\Contracts\Pagination\LengthAwarePaginator
     */
    public function getAll($nbrPages, $parameters)
    {
        return User::with ('ingoing')
            ->orderBy ($parameters['order'], $parameters['direction'])
            ->when (($parameters['role'] !== 'all'), function ($query) use ($parameters) {
                $query->whereRole ($parameters['role']);
            })->when ($parameters['valid'], function ($query) {
                $query->whereValid (true);
            })->when ($parameters['confirmed'], function ($query) {
                $query->whereConfirmed (true);
            })->when ($parameters['new'], function ($query) {
                $query->has ('ingoing');
            })->paginate ($nbrPages);
    }
}

This structure makes use of the config file parameters :

<?php

return [

    'users' => [
        'order' => 'created_at',
        'direction' => 'desc',
        'role' => 'all',
        'valid' => false,
        'confirmed' => false,
        'new' => false,
    ],
    'posts' => [
        'order' => 'created_at',
        'direction' => 'desc',
        'new' => false,
        'active' => false,
    ],
    'contacts' => [
        'new' => false,
    ],
    'comments' => [
        'new' => false,
        'valid' => false,
    ],

];

The structure of the database is as follows:

Schema::create('users', function(Blueprint $table) {
    $table->increments('id');
    $table->timestamps();
    $table->string('name')->unique();
    $table->string('email')->unique();
    $table->string('password');
    $table->rememberToken();
    $table->enum('role', array('user', 'redac', 'admin'));
    $table->boolean('valid')->default(false);
});

I'm trying to understand these methods: whereRole , whereValid and whereConfirmed , I searched the entire project and did not find the structure of these methods, how does Laravel build these methods?