object not found error while trying to open a web page

This is my first post in this forum, I am learning Laravel and have completed just few lectures. I have several questions.

1. what is the first and second parameter in Route function?

Route::get('/about','PagesController@about'); Route::resource('posts', 'PostController');

1. I am getting object not found error when I try to open a page url :: My web.php file code ``<?php

Route::get('/about', function () { return view('pages.about'); });

Route::get('/about','PagesController@about');

Route::resource('posts', 'PostController');``

PostController.php code ``<?php

namespace App\Http\Controllers;

use Illuminate\Http\Request;

class PostController extends Controller { /** * Display a listing of the resource. * * @return \Illuminate\Http\Response */ public function index() { return view('posts.index'); }

/**
 * remaining code blocks
 */

}``

Please see the uploaded image for my folder structure. https://ibb.co/nMYLjy