WordPress has a modular structure. The three different types of pages rendered are broken down into different parts with separate php code. To properly understand WordPress (or any LAMP based CMS website) one needs to appreciate that it is after all a play between the php code, the CSS stylesheets (which control the theme components and look and feel) and the database (which stores everything – data, pics and other files).
The three types of pages that WordPress is divided into are:
Single Post page
Multi-post page (category page, archive page or search)
Now, each of these pages have typically these components within their code. Remember: We are taking of a plain and vanilla structure. We could get more complicated structures to do different things. But this is the basic minimum!
WordPress world is full of great paid themes and it takes a lot of money to get an amazing blog magazine going. I know I have spent money on those. And, with so many themes being licensed only for one...