what is attribute in laravel eloquent relationship code example

Example 1: laravel belongs to

<?php

namespace App\Models;

use Illuminate\Database\Eloquent\Model;

class Phone extends Model
{
    /**
     * Get the user that owns the phone.
     */
    public function user()
    {
        return $this->belongsTo('App\Models\User');
    }
}

Example 2: laravel how to query belongsTo relationship

$movies = Movie::whereHas('director', function($q) {
    $q->where('name', 'great');
})->get();