For each of the supported languages, the Revit software contains translations for the user interface.
Revit does not use language packs. Instead, the base language for the software is determined as follows:
In a default Revit installation essential language content packs for the 14 supported languages in Revit will be installed. Essential language content is option within Custom Install workflows.
Optional language content packs can be added directly to Revit installation within Custom Install workflows. Alternatively, the option language content packs can be downloaded from Autodesk Accounts and installed at a later time.
For online help (when connected to the Internet), by default, users go to the Revit help site for the language selected for the Revit software. If you always want to access online help for a particular language, regardless of the language being used for Revit, edit the Revit.ini file to define the OnlineHelpLocale setting in the Documentation section.