what is left and right join in laravel code example

Example 1: left join laravel

$users = DB::table('users')
            ->leftJoin('posts', 'users.id', '=', 'posts.user_id')
            ->get();

$users = DB::table('users')
            ->rightJoin('posts', 'users.id', '=', 'posts.user_id')
            ->get();

Example 2: join in laravel

$subCategories = Subcategory::join('categories', 'subcategories.category_id', '=', 'categories.id')
                              ->select('subcategories.*', 'categories.name AS cname')
                              ->orderBy('id', 'desc')
                              ->get();