A wiki is a collaborative website: a page or collection of web pages designed to enable anyone who accessit it to contribute or modify content. Wikis support hyperlinks and have simple text syntax for creating new pages and cross-links between internal pages. The user only needs access to a web browser. Wikis can be useful as shared social spaces for team members who work remotely. They can be used as collaborative authoring tools. There is one document to work from rather than multiple copies circulating around the team. Contributing authors can percolate their ideas longer and include more ideas in the draft as a result of more frequent editing sessions. Access can be controlled; wikis can be private to an individual or group and they can be read-only for sprecified groups.
Wikis in plain English A short explanation of wikis and how they can used to coordinate a group
The most well-known example of a wiki is Wikipedia http://www.wikipedia.org/
As a password-protected space for a researcher and their group which can be used:
There are a number of wiki packages available on the web
WikiMatrix helps you find the wikis that match your personal needs and allows you to compare different wikis. http://www.wikimatrix.org/
Here are other types of collaborative editing tools: