I have never ever seen this filter, but I suspect this is related to if Google Search will take other languages, equate them for you, and include them in the search results.This was identified by Praveen Sharma and posted on Twitter – here is his screenshot: Google has an old help file that is not live on the existing site, however is readily available in the Wayback device that describes cross-language search results as, pages are picked based on our analysis of where the most significant information gaps exist in various languages, and the quality and significance of a candidate page to the users question. Cross-language search activates only when Google cant find a top quality response in the users query language.So I presume this is Googles method to show you when Google does this in Search and if it affects your pages or not.Have you seen this filter before in Search Console?Forum conversation at Twitter.