A wiki is a collection of webpages that can be modified by anyone who has been given access to it. Some wikis are open to anyone with a web connection — others are tightly controlled by small project teams. Wikis enable groups to collaborate online — contributors can add and edit pages to the wiki and view changes made by other users and roll back to previous versions. Contributors do not need to know how to write web pages as the editing is usually done with a simple editor which allows basic text formatting, inserting images, uploading documents and creating hyperlinks to other websites and resources.