The sidebar contains information that relates to the page you are viewing. It features a link to page revision history, a watchlist star that lets you put the page into your watchlist or remove it, and three colored boxes displaying Tags, Incoming Links, and Attachments.
Toggling the sidebar. Clicking the V shape in the right-hand corner of the page will make the sidebar vanish. Click the > to bring back the sidebar.
The sidebar boxes are presented in the following order:
Tags. This is a list of all the Tags that have been applied to the page.
Incoming links. This is a list of all the pages that have a link to the page you are currently viewing.