Generally speaking, a wiki is a collaborative, informal technology for organizing information on websites.
The communication between you and a wiki is going in two directions - two-way communication. That is, in contrast to a "normal" website that you are usually only able to read, a wiki enables you not only to read but also to easily edit information. Since the authoring is distributed several users have the possibility to improve the content by contributing knowledge and experience.
And do not fear to make mistakes! Since a wiki is version controlled, you can always roll back to an earlier version of the text.
Wikis have various degrees of freedom - different access rights for different users. Some are totally free to read and edit like Wikipedia while others are semi-open like the Encyclopedia of Earth and BioMineWiki (free to read but somewhat restricted to edit). Some are closed like for example many enterprise wikis.
This citation by Joe Kraus - one of the founders of the wiki company JotSpot - illustrates some reasons for using a wiki:
“We realized we needed a tool to help us organize our thoughts or we'd quickly become overwhelmed. So Graham set up a wiki. I was hooked because it immediately changed the way we worked together. Everything was kept in one place, not locked in email threads or on different computers. We could both make changes to the same document, without having to know HTML (well, without me having to know HTML). After twenty minutes of using a wiki, I was convinced that they were like the Internet in 1993 -- useful, but trapped in the land of the nerds.” 
Wiki strengths and characteristics
- Informal and easy to use.
- Edit and read through browser anytime by anyone with access rights.
- A wiki-page comes without any structure. Chaotic but flexible! It is born as a blank page - a free-form not setting any artificial limits on content. Text, structure and hierarchy will progress perpetually and develop in an ad-hoc way depending on the purpose and finally on the community of users.
- Wiki-pages are non-linear hypertext. There is not one way to explore a wiki but several arbitrary entry points depending on how the users create hyperlinks and connect pages with each other.
- All wikis start off as a single blank page. The name of the article is actually also a hyperlink – the name is embedded in a hyperlink.
- The community owns the pages; anyone can change the work of others - that is - no ownership-hierarchy.
The simplest, on-line database
Ward Cunningham introduced the world’s first wiki-software 1995 and described it as the "simplest on-line database that could possibly work". Since then, wikis have become more and more common. The most notable one is probably Wikipedia.
The database contains a collection of structured data and keeps track of the relationships between the data. Examples of such relations between data may be what account rights does a certain user have or what webpages link back (point) to a certain webpage. Also, the idea with a database is usually to share the information in the database by a community of users so that the data can be used interactively – a large number of contributors can add material as well as read it.
The wiki-software will enable non-technical users to edit and retrieve information from the database in an easy way. The wiki allows non-technical users to make changes to an existing website with little or no training. So a wiki is a tool for collaboration and usually involve a community of users working together through the wiki.
Like Wikipedia this site is aimed for two-way communication (read and edit). The major difference from Wikipedia is the scope of BioMineWiki. Also, unlike Wikipedia, not everybody can register to edit articles.