Wikipedia defines Wiki as "a website that allows the creation and editing of any number of interlinked web pages via a web browser using a simplified markup language or a WYSIWYG text editor. Wikis are typically powered by wiki software and are often used collaboratively by multiple users. Examples include community websites, corporate intranets, Knowledge management systems, and note services. The software can also be used for personal notetaking".
Wikis can be used for different purposes. Some allow control over different functions (levels of access). For example editing rights gives you the options of changing, adding or removing material. Others may permit access without enforcing access control. Other rules can be imposed for organizing content.
Ward Cunningham, the developer of the first wiki software, WikiWikiWeb, originally described it as "the simplest online database that could possibly work." "Wiki" (pronounced [ˈwiti] or [ˈviti]) is a Hawaian word for "fast".
Nowadays, there are millions of Wikis for different purposes, many of them for the purpose of teaching different subjects or topics. Among the most famous wikis is Wikipedia, http://en.wikipedia.org/wiki/Main_Page. which is a collaborative encyclopedia on-line. Experts from all around the world offer their expertise in order to feed this powerful tool with their knowledge and in this way people can benefit and get information in a very fast way about different topics in a huge number of languages. Another important one is WikiEducator http://wikieducator.org/Main_Page which aims to be an evolving community for learners based on collaborative free learning. Wikis are very powerful artifacts as far as working collaboratively in the TEFL class is concerned. A Wiki can be used by teachers at different levels and with different learners needs, from children to adults, it can be adapted for designing projects for students, it allows to share relevant information about so many topics and therefore, knowledge can be shared and meaningfully built up.