!!! Overview
[{$pagename}] is an [HTTP Request] [HTTP Header Field] advertises which [languages] the [client] is able to understand, and which [locale] variant is preferred.

[Language-Tag] is a [Language Code] for a [Language] usually used with [HTTP] and describes more about [{$pagename}]

!! More Information
There might be more information for this subject on one of the following:
[{ReferringPagesPlugin before='*' after='\n' }]