Proxying allows you to map a URL path in a virtual server's website to one or more destination URLs. This is typically used to make Ruby on Rails applications served by multiple Mongrel instances available under a URL path in the server's website. It can also be used to make other webservers such as Tomcat available via a URL path on your website.

For example, you might map the path `/radiant` to the URLs `http://localhost:3001` and `http://localhost:3002`, which are the ports for two Mongrel instances serving the same application running on your Virtualmin system.

Only systems that have the `mod_proxy_balancer` Apache module installed can map a path to multiple URLs. Others that only support Apache's regular proxy module can forward a path to just a single URL.