Hi Tim,
The "allowed languages for translation" permission grants a user permission to translate AtoM content only in the selected language or languages. The user will also need at least "contributor" permissions so they can edit content. When the user switches AtoM to one of the languages they can translate, they will be able to edit content (e.g. descriptions, authority records, etc.) in that language and translate content if the original language is different from the current language.
Note that adding a user to the "translator" group allows them to translate content in *any* language, so the "Allowed languages for translation" setting is ignored in this case.
Best regards,
David Juhasz (he/him)