The menu admin page can be found under the "Site Building" admin area.
When you go to the page for configuring your menus, you will see a listing of the menus available plus tabs for creating new menus and the settings for the menu.
Sites typically come standard with these menus: Navigation, Primary links, and Secondary links.
Navigation is the menu that shows in the sidebar and is titled by your username. Read about the Nav menu here.
Primary links is the menu most often used in the banner area.
Secondary links can either be a completely different menu or you can assign to it the same items as the Primary links menu. This allows you to show child items of the Primary links. You can read more about this on Drupal.org (opens in a new window).
You can edit and add to your menu system from here:
As you can see, you can easily disable or rearrange items for any menu.