Rewrite URL with folder name

Hi,

My Nginx Reverse proxy IP is 192.168.1.10 and my httpd web server IP is 192.168.1.15 which is behind the Nginx Reverse Proxy. All I need is, when I type in the browser http://192.168.1.10/test it should serve the page from the web server http://192.168.1.15/app but in my browser it should display as http://192.168.1.10/test and not http://192.168.1.10/test

Thanks in advance