what is the use fails method in laravel code example

Example 1: laravel validation

/**
 * Store a new blog post.
 *
 * @param  Request  $request
 * @return Response
 */
public function store(Request $request)
{
    $validatedData = $request->validate([
        'title' => 'required|unique:posts|max:255',
        'body' => 'required',
    ]);

    // The blog post is valid...
}

Example 2: laravel validation

"foo" => "Your input was invalid!",

"accepted" => "The :attribute must be accepted.",

// The rest of the validation error messages...