What is the url behind proxy_pass of nginx reverse proxy? The 127.0.0.1 written in the example below represents the local machine? Represent yourself? What is the function?

    location / {
        proxy_http_version       1.1;

        add_header               Strict-Transport-Security "max-age=31536000; includeSubDomains; preload";
        add_header               X-Frame-Options deny;
        add_header               X-Content-Type-Options nosniff;
        add_header               Content-Security-Policy "default-src 'none'; script-src 'unsafe-inline' 'unsafe-eval' blob: https:; img-src data: https: http://ip.qgy18.com; style-src 'unsafe-inline' https:; child-src https:; connect-src 'self' https://translate.googleapis.com; frame-src https://disqus.com https://www.slideshare.net";
        add_header               Public-Key-Pins 'pin-sha256="YLh1dUR9y6Kja30RrAn7JKnbQG/uEtLMkBgFF2Fuihg="; pin-sha256="aef6IF2UF6jNEwA2pNmP7kpgT6NFSdt7Tqf5HzaIGWI="; max-age=2592000; includeSubDomains';
        add_header               Cache-Control no-cache;

        proxy_ignore_headers     Set-Cookie;

        proxy_hide_header        Vary;
        proxy_hide_header        X-Powered-By;

        proxy_set_header         X-Via            QingDao.Aliyun;
        proxy_set_header         Connection       "";
        proxy_set_header         Host             imququ.com;
        proxy_set_header         X-Real_IP        $remote_addr;
        proxy_set_header         X-Forwarded-For  $proxy_add_x_forwarded_for;

        proxy_pass               http://127.0.0.1:9095;
    }