Wordpress is an open source PHP content management system with many free templates and plugins available. It uses template files like header.php, footer.php, and page.php to control layout and design, and includes template tags to dynamically output content. Custom functions can be added in the functions.php file to control business logic.

1.  Wordpress is a php based CMS( Content Management System )
 Open source
 Out-numbered free templates and plugins for easy development
 You can override any template functionlity

3.  The template file names are pretty logical
Quick overview of some template files
• header.php
• footer.php
• page.php
• single.php
• index.php
• sidebar.php

4.  Template tags let you insert dynamic content into your templates.
Include/function tags - Used to grab and display information or execute other
template files
<?php the_date(); ?>
<?php home_url(); ?>
<?php blog_info(); ?>
<?php wp_list_pages(); ?>
Conditional tags – Used to grab and display content depending on what page it
is and what condition it matches.
is_home();
is_single();
is_page();
is_category();

5.  Add a credit to the footer that uses include tags and a conditional tag

6.  What your template files need?
First, a name ( on top of your file )
<?php
/*
Template Name : [ Type your template name here ]
*/
Second, at least these 2 include tags
<?php get_header(); ?>
<?php get_footer); ?>
Last, any other content tag which you want to add

7.  You need to create your own function.php
 This file will controls almost all your business logic

8.  Magento
 Zendcart
 Drupal
 Joomla
and many other