The meta information of many different files can contain a piece of information called Language. It appears in archives as well as images, videos, audio files and of course documents and e-books. The meta information defines exactly what the name suggests, the language of a file. However, it might define different instances of Language in different kinds of files.
In documents, e-books and other text-based files, the Language metadata define the Language of the text inside the file.
In audio and video files, however, it most of the times refers to the language of the audio data and in rare occasions of the subtitles. The latter is usually defined separately though.
The values given for the Language metadata are usually made up of the language code of the respective Language. They can be represented in different forms, e.g. “eng” for English or “en-us” for English spoken in the USA. In many cases, the value can be defined as “und”, however, which means undetermined and thus referred to the Language not being set for this file.
The Language can be specified for specific parts of the file as well and is often also titled accordingly. This includes, for example, tracks, media or channels.