Themes are skins for your site that allow you to change the look, feel, and general appearance. You can use themes contributed by others or create your own.

Placing downloaded and custom themes in this directory separates them from Backdrop core's themes. This allows Backdrop core to be updated without overwriting these files.

Contributed themes from the Backdrop community may be downloaded at https://www.backdropcms.org/themes

It is safe to organize themes into subdirectories to ensure easy maintenance and upgrades. Is highly recommended to use Backdrop's sub-theme functionality to keep the code for related themes separated.

In multisite configuration, themes found in this directory are available to all sites. Alternatively, the sites/your_site_name/themes directory pattern may be used to restrict themes to a specific site instance.

Refer to the "Developing Themes" section of the developer documentation on the Backdrop API website for further information on customizing the appearance of Backdrop with custom themes: https://docs.backdropcms.org/documentation/developing-themes.