Subweb-Subdomain?

What is the difference between a "Sub-Web" and a "Sub-Domain"? We've recently received a few emails in the Mentor community (http://www.htmlgoodies.com/mentors) that suggest that at least in some people's minds these two are interchangeable. They certainly are not, and so a little clarification seems called for.

First, let's describe a sub-web (or subweb). As a matter of fact, there is no such thing! The term has been coined, however, by the folks at Microsoft. Let's explain. On the Internet there is a World Wide Web. You already knew that, but think about it for a moment -- there is a World Wide Web -- one web -- the Web. The Web is made up of a collection of a large number of sites -- Websites. Sites are a collection of pages, organized in some fashion, that have related subject matter. One such site is HTMLGoodies.com. HTML Goodies is organized into a variety of sections, each of which contains a number of Web Pages. Some of the folks at Microsoft, however, started talking about "webs" when referring to "websites". For example, in FrontPage you "Open Web" to open up a website.

Taking things a step further, FrontPage allows a site to have a theme applied, such that every page within the site uses a color scheme, button style etc. defined for the site. One change to the theme and the whole site has a new appearance. This is a more comprehensive method than is provided by the use of Cascading Style Sheets since every page within the site is automatically affected, whereas individual pages must specify whether or not they will follow a CSS specification, and if so, which one they will follow.

Since the FrontPage theme is automatically applied to every page within the site, the possibility of having a section with different theme would be precluded. That would not be good! To solve the problem, there is a feature within FrontPage that allows a section (contained within a folder, or directory) to be converted into a web(site) in its own right. It is not seen as another site by the server, however, and so is known as a "subweb" of the current web(site). If you have the parent web open in FrontPage and click to go into the subweb, FrontPage opens it in a new window, strengthening the impression that you are dealing with a separate entity. In the new window, you can treat the subweb as though it was a separate website with its own theme, etc..

A sub-domain, on the other hand, is very definitely a real thing.

This will take a little explaining, so please bear with me as I will have to start at the top and drill down to get to this one!