The side menu (or secondary navigation) is located on the right-hand side of the page for content types that can be added to the menu, such as Basic Page and Structured Page. It is derived from the Main menu structure, but only displays the siblings and children of the current page. As you navigate deeper into the site the side menu changes to be contextual to the page you are viewing.

Side menu's help users orient themselves when they land directly on a page deep in a site.