WordPress users may install and switch between 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 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 (Cascading Style Sheets) 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 should be purchased 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.