WikipediaWikipedia is a free encyclopedia.
Regarding the whole Wiki phenomenon, Wired Magazine has run an incomparable four-page article and I will pick up a few bits of information from it. That article goes over the history and evolution of Wikipedia, what exactly "Wiki" is, etc. However I will concentrate only on Wikipedia and only on the present-day Wikipedia.
How is Wikipedia different from others?
Unlike Encarta Online and Encyclopedia Britannica, Wikipedia is 100% free of any kind of charge. Also unlike Encarta and Britannica which offer 4500 and 80000 articles respectively, Wikipedia has an assemblage of about 500000 articles. Six times as many as Encarta and Britannica put together! Plus, there are no "Pay to read more" links or any advertising of any sort. In all fairness, they do need money to run (maintaining servers, staff, etc.) and for that they have a little link on the left that says "Donations", where people can go and give as much as their pockets can afford. However, they never ask you for donations.
Also, while Encarta and Britannica employ a few thousand "intellectuals" to do their article-writing and researching, Wikipedia taps into each and every human being who has Internet connectivity and wants to write for the encyclopedia. More on this when I explain how Wikipedia works, up next.
How does Wikipedia work?
You can go to any article on Wikipedia, click on a link called "Edit" or "Edit this page", make any change or addition in the text that you deem correct, and click Save. The article gets instantly altered. You don't need to create an account and sign in. You just need to click "Edit", make the changes, and click "Save". It's that simple. Similarly, you can search for something in Wikipedia and if you don't find it, you're presented with a link that says "create an article with this title", and if you click it, you're taken to a page that doesn't look quite unlike a Blogger : Create New Post page. You write your article, click "Save" and it's instantly available to the rest of the world. This is how I came to write my article on Impulsive Highlighting.
All this of course poses two huge problems: firstly, if anyone can post anything, how do you know that the information on the encyclopedia is true? Well, the short answer is that you don't. Wikipedia has slightly lower accuracy rating than the paid encyclopedias. But the good thing is that if you find any entry lacking in substance or one that has incorrect facts and figures, you can modify it then and there. The second problem is vandalism: internet graffiti. And this is not a form of art. However, this is mainly prevented because there are more good people than evil people and any bad edits to the Wikipedia are usually reverted in about 1.7 minutes! Such is the dedication of the authors and administrators. Anyway, the good guys are helped by the fact that there is a thing called the "watchlist" for users to which they can add articles which they would like to monitor. So if any change is made to those articles, they're notified.
That, in short, is Wikipedia. Though you should definitely go and read that article on Wired Magazine.