Wikis are available in public repositories with GitHub Free, and in public and private repositories with GitHub Pro, GitHub Team, and GitHub Enterprise Cloud. For more information, see "GitHub's products."
You can use a wiki to share detailed, long-form information about your project.
You can host documentation for your repository in a wiki, so that others can use and contribute to your project.
You can add and edit wiki pages directly on GitHub or locally using the command line.
You can add a custom sidebar or footer to your wiki to provide readers with more contextual information.
You can add images and links to content in your wiki, and use some supported MediaWiki formats.
Because wikis are Git repositories, every change you make is a commit that you can view.
You can disable your repository's wiki.
Only repository collaborators can edit a public repository's wiki by default, but you can allow anyone with a GitHub to edit your wiki.