SEO region is a recommendation for search engines (like Google) to display pages in a particular language in a specific region for those users who speak that language. If you have created a multilingual site, if necessary, you can specify the SEO region for each site's language version. For example, if you have a language version in the German language, you can select for search engines which region this language version belongs to, e.g., to the "Austria" region. This way, search engines will try to display the German language version's pages for German-speaking visitors in Austria.