What does location @fallback { proxy_pass do in the nginx config?

Hi,

In the nginx.ssl.conf file it has these three locations

 location / {
        proxy_pass      http://127.0.0.1:8080;
        location ~* ^.+\.(jpg|gif|bmp|ico|svg|tif|tiff|css|js|htm|html|ttf|otf|webp|woff|txt|csv|rtf|doc|docx|xls|xlsx|ppt|pptx|odf|odp|ods|odt|pdf|psd|ai|eot|eps|ps|zip|tar|tgz|gz|rar|bz2|7z|aac|m4a|mp3|mp4|ogg|wav|wma|3gp|avi|flv|m4v|mkv|mov|mpeg|mpg|wmv|exe|iso|dmg|swf)$ {
            root           /home/dave/web/gldn.page/public_html;
            access_log     /var/log/apache2/domains/gldn.page.log combined;
            access_log     /var/log/apache2/domains/gldn.page.bytes bytes;
            expires        max;
            try_files      $uri @fallback;
        }
    }

    location /error/ {
        alias   /home/dave/web/gldn.page/document_errors/;
    }

    location @fallback {
        proxy_pass      https://78.110.163.102:8443;
    }

What does the last one do ?

Is this “fallback” necessary ?
Do I need to be using port 8443 ?

Thanks