When you add a repository to Bitbucket, you also get a wiki. The wiki is a simple place to keep documents. Some people use it as their project home page. The wiki is a Mercurial/Git repository, so you can clone it and edit it like any other source files For example, take a look at the TortoiseHg wiki on Bitbucket.
Supported Markup Languages
In some cases, you can use a Bitbucket macro or the Bitbucket markup to do the same thing. The Bitbucket markup works in all languages; The Bitbucket macros work only with Creole markup.
Detailed Wiki How To Guides
The following pages provide detailed information on using a Bitbucket wiki.