What is WordPress?
WordPress is a free and open-source content management system (CMS) based on PHP and MYSQL. To function, WordPress has to be installed on a web server, which would either be part of an Internet hosting service or a network host in its own right. WordPress has a web template system using a template processor. Its architecture is a front controller, routing all requests for non-static URIs to a single PHP file which parses the URI and identifies the target page. This allows support for more human-readable permalinks.
WordPress users may install and switch between different themes. Themes allow users to change the look and functionality of a WordPress website without altering the core code or site content. Every WordPress website requires at least one theme to be present and every theme should be designed using WordPress standards with structured PHP, valid HTML (Hyper Text Markup Language), and Cascading Style Sheets (CSS). Themes may be directly installed using the WordPress “Appearance” administration tool in the dashboard, or theme folders may be copied directly into the themes directory, for example via FTP. The PHP, HTML and CSS found in themes can be directly modified to alter theme behavior, or a theme can be a “child” theme which inherits settings from another theme and selectively overrides features. WordPress themes are generally classified into two categories: free and premium. Many free themes are listed in the WordPress theme directory, and premium themes are available for purchase from marketplaces and individual WordPress developers.