A wiki is a term for websites (or hypertext documents more generally) that allow users to add content similar to Internet discussions, but also allow them to change existing content; in a figurative sense, a wiki is software that creates such sites.
Originally, the term wiki was used quite the opposite. A wiki was a type of software, and wiki-based sites were referred to as wiki-sites. Gradually, the meaning of the word wiki was transferred to the resulting website, and the term wiki-software was introduced for the platform used.
In a narrower sense, Wiki (with a capital "W") and WikiWikiWeb are sometimes used as a reference to the Portland Pattern Repository, the first wiki. Proponents of using this meaning recommend using a small 'w' to distinguish the general meaning discussed here.
The name of the wiki comes from Hawaiian, in which it is a term for "fast", resp. "very fast".
Sometimes the terms wikiwiki or WikiWiki are used instead of wiki.
A wiki allows you to create documents collectively using a simple markup language using a web browser. One page in a wiki is called a "wiki page," while a whole group of pages, which are usually heavily linked, is called a "wiki."
One of the defining characteristics of wiki technology is the easy creation and updating of pages. In general, no checks are made before the site is accepted, and most wiki systems are open to the public - or at least to anyone who has access to the wiki server. Usually, user registration is not required either.
Pages and their edits
In traditional wiki systems, each page is represented in three ways: HTML code, the page as a result of the browser displaying this code, and user-editable source code, from which the server generates HTML code. The latter format, known as wikitext, is written in a simplified markup language, the style and syntax of which may vary from implementation to implementation.
(Excerpt from the book of the Isaac Asimov Foundation, translated by Viktor Janiš - used with permission)
Some modern wiki systems use a different method: they provide WYSIWYG editing, usually through ActiveX controls or plugins, which translate graphically generated formatting instructions such as "bold" and "italic" into corresponding HTML tags. In these implementations, saving changes means sending a new HTML version of the page to the server, even if the user is shielded from these technical details, because the markup is generated transparently. Users who do not have the necessary plugin can usually still edit the page, usually by directly editing the line HTML code.
The formatting instructions that wikis allow vary greatly depending on the wiki engine used. Simple wiki systems allow only basic text formatting, while more complex ones have support for tables, images, formulas, or even interactive elements such as surveys and games. For these reasons, efforts are currently being made to define the Wiki Markup Standard.
Links and site creation
A wiki is a real hypertext medium with nonlinear navigation structures. Each page usually contains many links to other pages. Hierarchical navigation pages often exist in larger wikis, but they do not have to be used. The links are you