Taxonomy
Taxonomy is the description, subdivision and arrangement of people, things or items into groups and categories. Taxon is another word for group.
An example of applying taxonomy is assigning categories, labels and/or tags to a website's content (text pages, news articles, etc.). Adding such meta-information can help structure and make information findable. Making interrelationships between categories and groups helps classify information within a database into a hierarchical structure.
A practical application of taxonomy within a website is to automatically format a table of contents, provide a search function or display a tag cloud. Taxonomy-defined relationships between articles and categories can also be used to find and display related information and pages.