Allow your user to see the map in different languages to make your app international. The language parameter determines the language of labels on the map. It does not affect any proper nouns, like the names of streets, plazas, etc. The list of the supported languages can be found at Default View Mapping.
Sample use case: You want to have all labels only in British English.
To change the language for the map:
Map labels in English
Map labels in Russian
Map labels in Dutch