A reverse proxy is a server, that sits in front of other web servers. It forwards requests to those web servers. It can help increase security, maintainability, performance and reliability in some cases.
A reverse proxy can be used to increase security in some important ways. You can have the proxy handle SSL and therefore have your requests from the browser to the client be secured. The connection from the reverse proxy to the webserver is still unencrypt, but that is normally a local connection.
Furthermore, a reverse proxy is able to require a login before forwarding the requests to the webservice. Therefore, even if the service itself does not have any protection implemented, you can still protect it with a password.
A Reverse Proxy can also be used to cache certain requests, minimizing the load on your actual web server and increasing the speed for the client doing to the request. This lends itself especially well for simple websites that do not rely on databases or other software to show it’s content.
There are certain Reverse proxies that automatically detect webservices and assign it a subdomain. Setting up additional webservices will be easier and therefore you will have less to maintain.