Introduction

In Drupal there is a difference between menu and taxonomy (as of Drupal 6). The menu is a navigation system and taxonomy is a system to order content data: Menus is to arrive at content; Taxonomies are to order it.

A menu entry allows you to point directly to a node, like a page or a story, but you can also point to a term in a vocabulary, which would show you a summary list of stories or pages.

Managing your Menus

Screenshot of default Drupal 6 installation: Navigation menu: Administer - Site building - Menu

Start by going to the navigation menu and follow the links: Administer > Site building > Menu

Screenshot of default Drupal 6 installation: Navigation menu: Administer - Site building - Menu with menu highlighted

You'll end up at the Menus page

Screenshot of menu administration page

Next you will add a whole new menu

Screenshot of menu administration page: add a menu

There are three areas to add information to: menu name, title, and description

Screenshot of menu administration page: add a menu edit form
Menu name
The menu name has to be machine readable, which means that it can't have spaces, punctuation, and has to be lower case. This exists so that Drupal has an internal reference. As of Drupal 6: This text will be used for constructing the URL of the menu overview page for this menu. This name must contain only lowercase letters, numbers, and hyphens, and must be unique.
Title
The title is what you and other site users see and it can be anything you want
Description
Writing a description for your menu entry can be very useful to retain information about why the menu entry was created.

Once you have entered your information save your information.

More

Later you might consider using the taxonomy_menu module. It will add to your confusion, but it will be good when there are frequent changes in your vocabularies. It will make the difference between menus and categories almost completely disappear, because it allows you to make vocabularies appear as a menu. This way menus are generated automatically.

If you want hierarchical drop down menus, the nice_menus module might come in handy.