explain object class in c# code example

Example: c# objects

using System;

class Book
  {
    public string title;
    public string author;
    public int pages;
  }


class MainClass {
  public static void Main (string[] args) {
    Book book1 = new Book();
    book1.title = "Harry Potter";
    book1.author = "JK Rowling";
    book1.pages = 400;
    Console.WriteLine(book1.title);
  }
}