Mahna Mahna (Do doo be-do-do)

Drupal's categorization scheme, or taxonomy, is one of the traits that distinguishes Drupal from other content management systems. It is not necessary to use it in creating a site. A site may be created entirely out of various content types placed in a menu without additional categorization. To add, edit, or view the taxonomy for a site, click on the 'Categories' link in the administration menu. (Depending on your permissions, you may need to click Administer -> Content Management before you see the Categories link.)

The taxonomy in Drupal is made up of 'vocabularies' or groups of categories. Within a vocabulary there are categories called 'terms.' A vocabulary can be applied to one or more content types. For example, a common vocabulary might be 'Image Galleries.' This vocabulary would probably only be applied to the 'Image' content type and might contain the terms 'Landscapes', 'Portraits', 'Animals', etc. Then, whenever a user creates a new Image node, they are asked to categorize it into one of the Image Gallery terms.

A vocabulary can be optional or required. For example, if you wanted every Image to be part of one of the Image Galleries, the Image Gallery vocabulary would need to be required.

A node can be tagged in multiple vocabularies. Using the example above, you could create a second vocabulary called 'Location.' This vocabulary could also apply to Image nodes (in addition to other content types). Vocabularies can be single or multiple select as well; an Image could be put into more than one Image Gallery as well as being associated with one or more Locations.

Taxonomy is particularly useful in combination with views because a view may filter based on whether or not a node has a certain term associated with it. So, you could create a view of all Image nodes (a.ka. an Image Gallery) that are associated with the term 'Portraits'. Taxonomy terms are not node fields however, and thus are not as easy to display. Their primary function is for sorting.