The installation's own hostname. It belongs to no site; platform administrators run all sites there. In code, the site with the ID default. Concepts
Site
A context that answers on a hostname of its own, or under a main site's hostname at a path prefix, with its own content, settings, languages, menus and people. Concepts
Main site
A site that stands on its own: it answers on its hostname and inherits nothing unless told to. Hostnames and sub-sites
Sub-site
A site that belongs to a main site: it inherits from it and can be run by its people. It answers under the main site's hostname at a path prefix, like www.hydrion.example/uk, or on a hostname of its own. Hostnames and sub-sites
Path prefix
The first path segments under which a sub-site answers on its main site's hostname. Hostnames and sub-sites
One per-site value, like the site name or the theme. Settings are grouped in sections. Concepts
Layer
One source of a setting's value: settings.php, environment, language, the site's own value, the site type default, the module default. The highest layer that sets a value wins. Setting layers
Environment
A deployment stage, like staging or production, named on each server. A setting can hold one value per environment. Setting layers
Inherit
A site takes a setting's value from the site it inherits from: a sub-site from its main site, or the site chosen on its Inheritance section. The site type decides which settings, and whether the site may replace the value. Setting layers
Configuration override
A setting stored as the site's own value of a Drupal configuration key, like the site name. It applies on the site's address only. Setting layers
Setting plugin
The code that declares a group of settings and its form. Setting plugins
On a site's address, content of other sites answers "Not Found" and does not render inside pages. Content on sites
Language isolation
On a site's address, only the languages the site speaks exist. Languages
Site filtering
Listings and reference fields limited to the active site's content. Blocks and views
Per-site menu
A menu whose links differ per site while the menu itself is shared. Content on sites
Own version
A site's version of shared content; the content on the origin site is the original, and the origin site has no own version unless Overrides on the original is on for it. The mechanism and its settings are called content overrides, and the API calls an own version an override. Content overrides
Pin
A field a site's own version changed. It keeps the site's value until the site reverts it to the original. Satellite APIs
Aspect
Per-site data about content that belongs to a site's own version, like a URL alias, a menu link or sitemap settings. Content overrides
Clone method
What a site's clone gets of one content type: nothing, the same items, or copies. Clone a site
Cloning rules
A site's clone method per content type, the defaults of its clone form. Clone a site
Preview
A site's pages viewed from the hub at /preview/{site}. Preview