protected $guarded in laravel code example

Example: fillable vs guarded laravel

Mass assignment is a process of sending an array of data that will be saved to the specified model at once. In general, you don’t need to save data on your model on one by one basis,
but rather in a single process.
  In Laravel, fillable attributes are used to specify those fields which are to be mass assigned. Guarded attributes are used to specify those fields which are not mass assignable.