A wiki is a type of website which allows multiple users to create and edit any number of interlinking pages for viewing within a web browser using a simplified markup language editor.
Wikis may be created to serve a wide variety of functions, from simple personal note-taking to corporate information databases. Some wikis may be created to serve a specific purpose, maintaining a strict editorial code-of-conduct and limitations on accepted content (otherwise known as closed-purpose wikis), whilst other wikis may accept a wider variety of content with fewer rules and regulations (these are often referred to as open-purpose wikis).
By far the most prevalent example of wiki technology currently in use is Wikipedia, a closed-purpose wiki designed to serve as a collaborative encyclopedia. With over 15 million articles (over 3.2 million of which are written in the English language), Wikipedia has established itself as one of the largest and most popular sources of general reference material within the Web 2.0 zeitgeist. Since its launch in 2001 by founders Jimmy Wales and Larry Sanger, Wikipedia articles have been referenced in journalism, literature, academic studies, and even court cases. This wiki's cultural significance has also been a source of satire for social commentators; its content has been parodied by several comedians, and is often referenced in online comic strips and "geek humor".
Wiki technology was invented by Ward Cunningham, who began developing the first wiki, WikiWikiWeb, in the mid 1990s. The project was inspired in part by by the HyperCard application, a system developed by Apple prior to the World Wide Web which utilises a user-modifiable, flexible interface combined with database functionality; Cunningham had developed a stack of HyperCards for use with this platform in the late 1980's, making the wiki one of the many descendents of this early form of hypermedia technology. The name wiki comes from the Hawaiian word for “quick”.
Many people choose to host their wiki content via a wiki farm, due to the complexity of installing and hosting the software on their own server; wiki farms provide the functionality of a wiki (ease of creation and editing) with little of the technical fuss, usually in return for the hosting of advertisements on each page or some kind of monthly fee (similar to web hosting). Both commercial and non-commercial varieties of wiki farm exist; some of the most popular examples of wiki farms include Wikia, PBWorks (formerly PBWiki) and Wetpaint.
One of the most prevalent issues faced by wiki-based communities is vandalism, as the general culture of openness leaves many wikis open to abuse of this editorial freedom. Efforts to tackle vandalism without sacrificing an open editorial culture include making wiki pages easy to edit (and therefore easy to revert to a previously unvandalised version), as well as automatic vandalism detection (via bot scripts, similar to spam filters) and functions such as the ability to monitor the content of each edit (highlighting any changes made). Many wikis also require users to log in to an account prior to editing a page, or may record the IP address of an editor if 'anonymous' editing is permitted. As a result, the incidences of vandalism which do slip through this defensive net tend to be minor or surreptitious in nature (akin to other Internet pranks, such as a Google bomb, and generally referred to as trolling), which often requires manual detection by other keen-eyed editors. Wiki administrators may be able to protect (or even lock) pages within their wiki if they suspect a high risk of vandalism, as has often been the case with articles related to sensitive subjects, such as race, religion, politics, and sexuality, as well as articles about celebrities. Incidents have occurred in the past where members of political and corporate organisations have been found to be responsible for tampering with Wikipedia articles; such behavior is likely due to Wikipedia's popularity, in addition to the perception of online anonymity amongst article vandals.
Critics of Wikipedia cite this susceptibility to vandalism amongst their concerns regarding the wiki encyclopedia, along with accusations of inconsistencies, bias (such as anti-religious, pro-choice, and liberal bias), and unreliable content. However, a consistent feature across the majority of wiki sites, particularly those that host information, is a heavy emphasis on the presentation of verifiable cited primary sources, as well as the representation of a neutral point-of-view within articles. Due to concerns regarding the veracity of wiki articles, many teachers and academic lecturers discourage (or even outright prohibit) the use of websites such as Wikipedia amongst their students, in favour of primary or otherwise more "official" sources. Generally speaking, a wiki article - like any secondary information source, should be considered less a source of information than it is a corrolation of multiple sources of information which ought to be investigated and referred to in their own entirety, rather than cited based on the interpretation of the editor(s).