WordPress is a free and open-source content management system (CMS) based on PHP and MySQL. WordPress is installed on a web server, which either is part of an Internet hosting service or is a network host itself; the first case may be on a service like WordPress.com, for example, and the second case is a computer running the software package WordPress.org.

WordPress is built on PHP, supported by MySQL and integrates with a variety of features and tools used to design, develop and manage websites. WordPress provides easily deployable proprietary and third-party themes, plug-ins and widgets that facilitate the integration of third-party code snippets, providing enhanced user features, including the ability to customize code, build search engine friendly internal-links and tagging.

In 2001, Matt Mullenweg and Mike Little co-founded WordPress, launching it in May 2003 with the help of several core contributing developers. At that time, WordPress was merely a free blogging forum for users. Since then, WordPress has evolved to be a full content management system with widgets, plugins and customizable themes.

A WordPress Widget is a small block that performs a specific function. You can add these widgets in sidebars also known as widget-ready areas on your web page.
WordPress widgets were originally created to provide a simple and easy-to-use way of giving design and structure control of the WordPress theme to the user. Widgets can be easily dragged and dropped into a specific widget area. You can find the list of available widgets and widget areas by going to the Appearance » Widgets section in your WordPress dashboard.