The word "semantic" is one of those words people sort of understand, but not completely. Like "humility," it's a word that's hard to pin down. Most people don't really know what it means, which is ironic because it means meaning: "of or relating to meaning in language."

So, are we trying to build a "web of meaning"? Well, here we run into a similiar problem: "meaning" has many meanings. We use it to show intent ("I mean to please") or purpose ("I was meant for this job") or significance ("you mean everything to me"). We also use it when connecting a thing with its definition ("House is where people live", "Green means go"). This last sense is the one one we're after. Semantics is the study of "signs" and what they refer to. Put another way, semantics is the study of links.

"A piece of information is really defined only by what it's related to, and how it's related. There's really little else to meaning." Tim Berners-Lee, Weaving the Web

"But what a minute," you might say. "I thought the current web was all about links. Isn't that what hypertext is?"

Yes, the "non-semantic" web has links, but currently the links convey no real meaning other than "this thing has something to do with that thing." Sure, there's usually some English description like "editorial reviews", but this falls short for several reasons. For one thing, there's little consistency to these descriptions. One site says "reviews", another says "testimonials". Even worse, computers can't make sense of it. A human is required to interpret something as simple as "click to order" or "contact us".

So when we talk about adding "semantics" to the Web, we're really talking about adding consistent meaningful links that computers can understand. Of course this begs the question, "What is understanding?" For now let's be pragmatic and simply say, "able to use usefully." The rest is just too hairy.