Localization
XWiki has its own localization framework and tooling.
For developers
Since the set of translations in the XWiki ecosystem and in a running XWiki instance is huge the XWiki project has defined some translation keys naming and rules over the years to make easier to navigate through them and avoid common mistakes.
XWiki Standard has a list of officially supported locales corresponding to the list of locales for which at least one the XWiki Standard defined keys was translated and ideally also means that any process related to translations (Java level resource like dates are properly translated, translated content is indexed and searcheable, etc.) will work for those translations.
For translators
An online platform based on Weblate is provided to translators to make easier to contribe translations for XWiki Standard and contrib extensions registered on it.
For administrators
Here are some resources to understand better how https://l10n.xwiki.org works under the hood: