Web-server – How to list files under a URL to a directory on a web/HTTP server

A web server is something that serves you contents using the HTTP(S) protocol; it receives requests in the form "give me http://some.site.com/some/page?some=parameter" and sends back an answer that can be an HTML page or anything else that can be transferred over HTTP(S); that is, pretty much anything (see MIME for details).

More often than not, web pages will not be only static text files, but will be generated on-the-fly by the server using some server-side code developed by programmers; when a web site (or part of it) gets complex enough, it's common to define it as a "web application"; the term is very vague, and actually means "a web site with a dynamic-generated content". Sometimes, the web server and the application server are actually the same program (see IIS, or Apache with modules); other times, the application server is a full-blown different program (maybe even running on a different machine), which communicates with the web server to feed it dynamic contents while the web server manages HTTP requests and static contents; this is the standard practice for Java web sites.

A web service is a web application which follows some standards defined for exchanging requests and responses using XML; the idea here is that the web service is not going to be used by humans, but will be called by other programs (possibly being web applications themselves) and so it doesn't need to do fancy graphics or anything else, but just to provide the requested informations in a standardized way.

You could also do this using virtual hosts and setup Apache as a reverse proxy. This is how I have it setup where I work.

a.domain.com -> ProxyPass http://192.168.1.101
b.domain.com -> ProxyPass http://192.168.1.102

Checkout the documentation for ProxyPass and ProxyPassReverse.

If you just do a name based virtual host for both then you could add something like this to your virtual host definition (or replace localhost for your IP if your box will be hosting apache):

<Location />
    ProxyPass http://192.168.1.101
    ProxyPassReverse http://192.168.1.101
</Location>

Then in your friend's virtual host config

<Location />
    ProxyPass http://192.168.1.102
    ProxyPassReverse http://192.168.1.102
</Location>

You can also add ports to the ProxyPass directive if you don't want your friend to change firewall rules, service setting etc. Or you can even be a reverse proxy for another external IP address too.