Each Autodesk product is installed with a default language. A language pack is a mechanism used by some Autodesk products to provide another language for the user interface and the documentation. Each language pack contains only the text strings and documents required to support a user working in the specified language; it does not duplicate the core product software.
To run Autodesk Navisworks in another of the installed languages, you need to add one of the language selector arguments to the desktop shortcut. To be able to do this, you need to have installed at least one language pack during the Autodesk Navisworks installation process.
Language packs are about 200 MB in size, so they can be installed and uninstalled quickly. A single installed product can support several languages, enabling users to switch from one to another when required.