WordPress users may install and switch among 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,
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 (also known as the repository), and premium themes are available for purchase from
marketplaces and individual WordPress developers. WordPress users may also create and develop their own custom themes. The free theme Underscores created by the WordPress
developers has become a popular basis for new themes.