Etymologically speaking, semantics refers to the meaning of words and symbols
constituting a language, be it human language or a computer language.
As the Internet has evolved into the current world wide web, so will the web
slowly evolve into the Semantic Web, or a Web which is more meaningful to its human users.
When your current Internet browser saves passwords for your email ids that you type in so that you don't have to type in the password every time you
want to check your email on your home computer, you are dealing with a more intelligent
browser than what we had ten years ago. This is just one simple example of how web browsers
are becoming more user-friendly over time.
As time progresses, technologies which connect us to the web (primarily the web browsers
on gadgets ranging from your handhelds to your laptops) are going to become even more friendlier,
understand your needs even better, and serve the data / video / audio / information in a
cheaper / better / faster / more efficient manner. That, in a nutshell, is the idea of a
Semantic Web.
Currently, we are in a Web 2.0 world. As more and more people get on the Internet,
and as people switch more and more from print and TV etc. to the Internet, we would have moved on from the current Web 2.0 to Web 3.0. In other words, we will call the current World Wide Web the Semantic Web.