If language is set to "browser" the client/user browser language is used to choose from
available translation.
simply: one users browser speaks English -> YaCy responds in English, other users browser speaks French -> YaCy responds in French.
! To make a translation/language available you have to activate the language once !
(or manually use the utility class TranslateAll)
In ConfigBasic.html availabel translations are marked green on setting language=Browser
The client language is determined by http header Accept-Language (checked in DefaultServlet)