WordPress is a free and open-source content management system (CMS) based on PHP and MySQL WordPress is installed on a web server that is either part of an Internet hosting service or a network host in its own right. The first case may be a service like WordPress.com, for example, and the second case could be a computer running the software package WordPress.org. A local computer may be used for single-user testing and learning purposes.WordPress users may install and switch between different themes. Themes allow users to change the look and functionality of a WordPress website and they can be installed without altering the content or health of the site.
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 and Cascading Style Sheets (CSS). Themes may be directly installed using the WordPress “Appearance” administration tool in the dashboard or theme folders may be uploaded via FTP. The PHP, HTML (HyperText Markup Language) and CSS code found in themes can be added to or edited for providing advanced features. WordPress themes are in general classified into two categories, free themes and premium themes. All the free themes are listed in the WordPress theme directory and premium themes are available for purchase from marketplaces and individual WordPress developers. WordPress users may also create and develop their own custom themes if they have the knowledge and skill to do so.