A wiki is a type of website. The website is wiki-style. This is a website content management system (CMS) that makes Web pages freely and also editable by all authorized visitors. This site or Wikipedia are wikis.
That is to say that everyone (allowed) may modify, supplement and add pages to the site. It is usually found at the bottom of each page a small link “Edit this page” that allows anyone to edit the content of the page. Editing pages is easy and fast.
So wikis enrich gradually with the knowledge and information of each.
This is not necessary. The wiki does not generally require any knowledge of HTML. They allow, through simple conventions to format text (bold, italics, lists …). This allows the uninitiated to easily edit pages. And you do not even need special software: everything is done in your browser.