The bottomline first: It works.
"Imagine a world in which every single person on the planet is given free access to the sum of all human knowledge. That’s what we’re doing." - Jimmy Wales
For those who still don't get it what is being talked about, the subject of this post is Wikipedia and more specifically the English Wikipedia. The quote above is by the founder of Wikipedia, quoted in a Slashdot Interview.
What is Wikipedia?
In brief, Wikipedia is an encyclopedia. It is the world's largest encyclopedia and is growing at an extremely fast rate. With more than 1 million articles in English Wikipedia, it can be used as a single point reference to know from biography of Atilla the Hun to ingenuity of the Monty Hall Problem. What's more a lot of articles also have audio versions also, so one can also sit back and listen to them without having to read anything.
How stuff works?
This is where a complication begins. One would expect an encyclopedia to be written by experts; people who are associated with the topic in concern in great detail. However, Wikipedia is edited and maintained mainly by people like us, who are at best "Jack of few trades". And there is no deterrent to anyone's editing. Though registration is optional (though required for starting new articles), anyone can edit any page he/she wants. A big button shouting "edit this page" sits at the top of every article and besides every section welcoming you to edit and improve the articles.
So how does it work when there is no reason it should work? What stops people from vandalizing their hearts out, and corporations from using it as an advertisement board? Or in short, why should one use it at all when all one can expect is nothing more than few sentences of garbled text?
The reason is the philosophy behind Wikipedia and the founding principles of it. Wikipedia is based on three basic philosophies that are complimentary and non-negotiable. They are Verifiability, Neutral Point of View and No Original Research.
Verifiability means that only those things can be written in Wikipedia to which a source can be attributed as reference or can be observed by anyone without substantial effort. This directs people who contribute in Wikipedia to quote reputed sources of their articles and hence achieves good amount of reliability.
Neutral Point of View means that articles are to be written without any bias. This means howsoever you feel strongly about an article, you have to present it in neutral perspective without adding any personal opinions and flavors to the facts.
No Original Research means that you cannot write things in it that have not been previously reported by a reputed source. Hence Wikipedia is a source-based research and should not create primary sources.
It can be easily seen that with the strong content guiding policy like this, there is a platform created for things to prosper, given the right nurturing is given. It should be noted that Wikipedia strongly disallows copyrighted content (text, image or any form of creative work) to be written in it and licenses all works under GNU Free Documentation License.
Why the name Wikipedia?
Wikipedia is formed by joining the words "Wiki" and "Encyclopedia". All of you must be knowing what encyclopedia means, so only "Wiki" needs to be explained. "Wiki" is Hawaiian adjective meaning "quick". The philosophy behind adoption of this word is that a wiki-based system is easy to edit. One of the basic features of a Wiki is that it stores all revisions of the work, so that if anything bad happens (like vandalism or even a genuine mistake), things can be corrected. This can also be used to view how things were in the past, if relevant to the context, and mostly by editors to do things that will be discussed in details later. Wikipedia is based on a Wiki software called Media Wiki.
Although most of the editing part can be done by anyone, there are special things like deletion of article or blocking of compulsive vandals that can only be done by Wikipedia Administrators (known as sysops). They are elected on the basis of consensus among the Wikipedia community about the worthiness of the user in concern. Sock-puppetry (creating multiple accounts to support one's views) is strictly handled by Wikipedia and violators are usually banned.
The Wikipedia Mark-up
Wikpedia uses a markup similar to HTML though customized for a collaborative work with inter-related pages. In case one needs to link to a page in Wikipedia from a Wikipedia article, all that needs to be done is that to add double square brackets to the article name. For example, [[Indian Institutes of Technology]] will create a link to the article on Indian Institutes of Technology. There are similar easy ways of adding images and other useful features like bullets and tables. Although a lot of HTML codes work, their use is generally discouraged in favor of Wiki's own markup to provide consistency is article formats. Guides for Layout are available to make sure that there is little confusion as to how things are to be presented.
One of the serious problems that Wikipedia faces is vandalism of articles. However, the way Wikipedia is designed, vandalism is largely ineffective. Is is usually seen that most vandalism last less than 5 minutes! What's more, I can even quote this from my experience when I have seen vandalism getting reverted within a couple of minutes. This article can give you a good perspective of the issue being discussed.
The way vandalism is handled in Wikipedia is really commendable. First of all, since all previous revisions of the article in concern exist, once detected, its only a matter of couple of seconds that the article can be restored to its original state. Also, in order to check vandalism, there is a group of self-appointed people (I am one too), some 1000 in number, who check the recent changes taking place in Wikipedia from the Recent Changes Page. Coupled with a set of tools unknown to vandals and a lot of experience, they are able to weed out vandalism very effectively. In many instances, when I have reached a vandalized page within a couple of minutes, I see that someone has already come and corrected it. Amazingly, very little "garbage" goes through this filter. What does go through is still not spared. Most of the editors in Wikipedia (especially registered users) keep the pages edited by them in their watchlist. So, for example, if a person from Indore tries to advertise his business on Indore's Wikipedia page (which most likely a Recent Changes Patroller from Utah might not be able to qualify as vanity information), I get alerts of the changes. There are over 1000 articles in my watchlist even in the short span of less than 2 months in Wikipedia. With such multi-layered filtering, the vandalism/nonsense that does gets through is less than one PPM; something that can be considered very good.
Wikipedia has a lot of sister projects like Wiktionary, Wikinews, and Wikiquote. These complement Wikipedia's work as the resource for everything by being a repository of news, quotes, etc. Interlinking between sister projects is also easily done through the Wiki mark-up.
Behind the scenes
If you click on the "discussion" link at the top of any page, you will find what really lies beneath the calm and serene surface of Wikipedia. You will see a lot of discussions between the editors on what is possibly wrong with the article and how can it be improved. The way these discussions are carried out are also very structured and personal attacks are looked down upon. People are given feedback on their edits and suggestion from others (not directly related to the article) is also sought.
All users have their own profile pages and talk pages (for communication). This enables them to communicate with others more efficiently. Many user prefer to use "Userboxes" to tell things about themselves (like mine can be seen in my profile page's end and also directly here).
The good editors are rewarded by their peers for work, usually by giving a variety of Barnstars. Wikipedian are also known for their sense of humour and they lighten the mood when things start heating up in controversial topic debates. For example in an RfC (Request for Comments) over Kelly Martin's high-handed attitude in deleting userboxes that she felt are crap [sic] and should be deleted, also popularly known as the great userbox purge, a lot of people posted humourous stuff like an annoying pastel box.
A lot of things related to Wikipedia are prefixed by adding "wiki" before them. For example, any break from Wikipedia is known as a wikibreak, the stress caused by it is wikistress and the mood while editing Wikipedia is wikimood.
Some 1000 articles of English Wikipedia's are categorized as brilliant prose (Featured Articles). This is a extensive and rigorous process of review to establish that the article in concern conforms to high standards. In order to make an article into a Featured Article, it has to conform to a lot of strict guidelines on content and presentation. First there is a Peer Review where authors invite comments and suggestions from their fellow editors on how to improve the article. Once done, it can proceed for the Featured Article Review. Here experts suggest how the article can be fine-tuned to make it a brilliant prose. Once having achieved the FA status, the article also appears on the front page of Wikipedia.
Comparison with other Encyclopedia
Wikipedia, over time, has been compared to a lot of encyclopedia and the main things stressed are the quality of content and reliability. The points where Wikipedia failed to ensure reliability have been quoted often in the media. But I still use it as a primary source of reference because of my experience with it. When I read something about what was reported wrong in Wikipedia, I feel similar to reading about people who win in gambling. Millions of people buy tickets, but only those who win are featured in newspapers, etc. With a lot of opportunities for having an error, Wikipedia scores quite good as compared to other encyclopedias also. In a study, it was found that while Encyclopedia Britannica had on an average 3 errors per article, Wikipedia had 4; a feat considering it is just 5 years old. Other criticisms include unequal weightage of subjects, which I have to accept is true. As Wikipedia is evolving, whenever someone comes to an article he knows something about, he edits it. But almost never does he know everything about it. So the article waits for the next "expert" to come over and edit relevant sections. I feel its premature to compare articles randomly. If a comparison is to be made, it should be made between equals. Like a featured article in Wikipedia and in another encyclopedia. Although Wikipedia has the restriction of using free content only (it doesn't buy content like text, images, etc), I am quite sure wikipedia will be equal, if not better than the other encyclopedias. The reason behind my belief is that even the best of encyclopedias have a non-neutral point of view, or tend to find a diplomatic way out of the problem by either mis-representing facts or completely ignoring them. While in Wikipedia, care is taken that even minority view is expressed. Wikipedia does not work on voting, but on constructive discussions. If there is an evidence to include a content, it finds its way into the article.
The Real Bottomline
Even with so many potential dangers, Wikipedia scores quite well in both reliability and exhaustiveness because of the sheer large number of people editing it (more than 1 million registered users and innumerably more anonymous ones). Jimmy Wales once said that "Wikipedia is like a sausage: you might like the taste of it, but you don't necessarily want to see how it's made". It will apply to most of you but since I am a chef, I have to oversee it being made it to perfection.
(Note: The author is a Wiki-holic and averages around 35 edits a day.)