The Menus Module provides an easy drag-and-drop interface for configuring your menus.  Pages are set up in a hierarchical structure, allowing you to group pages by topic.  The drag-and-drop interface allows you to:

• move pages into different areas
• move pages up or down within the same area
• move groups of pages (pages plus their submens) at once

This interface is just a convenient UI for changing the parent_id and page_rank parameters of each page.