A wiki is a quickly editable Web site, usually one that allows either certain people or anyone from the general public to edit its content.

The very first wiki was the Portland Pattern Repository developed by Ward Cunningham. This wiki is also known as the Wiki Wiki Web, Ward's Wiki, and simply the Wiki. The most distinguishing feature of the Wiki (aside from its ability to let anyone quickly create and edit its content) was the use of "CamelCase" for automatic creation of wiki links.

The most famous wiki today is Wikipedia, and it's undoubtedly where new wiki users are most likely to gain their first experience. Or, if not Wikipedia specifically, then one that emulates Wikipedia's encyclopedic reference nature as much as it does the general wiki principles.

Quoting Wiki Design Principles from the PPR, a wiki should be:

• Simple - easier to use than abuse. A wiki that reinvents HTML markup ([b]bold[/b], for example) has lost the path!
• Open - Should a page be found to be incomplete or poorly organized, any reader can edit it as they see fit.
• Incremental - Pages can cite other pages, including pages that have not been written yet.
• Organic - The structure and text content of the site are open to editing and evolution.
• Mundane - A small number of (irregular) text conventions will provide access to the most useful page markup.
• Universal - The mechanisms of editing and organizing are the same as those of writing, so that any writer is automatically an editor and organizer.
• Overt - The formatted (and printed) output will suggest the input required to reproduce it.
• Unified - Page names will be drawn from a flat space so that no additional context is required to interpret them.
• Precise - Pages will be titled with sufficient precision to avoid most name clashes, typically by forming noun phrases.
• Tolerant - Interpretable (even if undesirable) behavior is preferred to error messages.
• Observable - Activity within the site can be watched and reviewed by any other visitor to the site.
• Convergent - Duplication can be discouraged or removed by finding and citing similar or related content.

This wiki (Wagn) enhances simplicity by using the TinyMCE editor for editing Basic-type cards, so most of the formatting available is in a modern-style word processor interface. Unlike many other wikis, there's no need to learn special wiki markup languages just to format cards.

Supporting incremental development, this wiki marks cards that don't exist yet in a color different from ones that do. Following a link to a card that doesn't yet exist allows you to create that card. (There may still be a bug here. Please read the note about this bug before creating cards.)

Most innovatively, Wagn's concept of cards nested within cards gives editors the ability to avoid duplication by splitting information off into other cards, then transcluding that content back into all the cards that need to include that content.

You can spot the cards you're permitted to edit if you enable the universal edit button for your Web browser. Because this site uses cards within cards, the universal edit button shows you your edit permission only for the root card of the page you're viewing. Use the button on any nested card's header bar to make it the root card.