laravel practice 21.intended method redirects the request to the last page

redirect() Providing a Examples of  intended the method that can be redirected to a page request attempts to access a page, and receives a jump address default parameters, when the last request record is empty, a default jump to the address.

public function store(Request $request)
    {
       $credentials = $this->validate($request, [
           'email' => 'required|email|max:255',
           'password' => 'required'
       ]);

       if (Auth::attempt($credentials, $request->has('remember'))) {
           session()->flash('success', '欢迎回来！');
           $fallback = route('users.show', Auth::user());
           return redirect()->intended($fallback);
       } the else { 
           the session () -> Flash ( 'Danger', 'We're sorry, your mailbox and password do not match' );
            return the redirect () -> Back () -> withInput (); 
       } 
    }