Taxonomy is a categorization framework used to identify or tag content. It sets the foundation for classification using a controlled vocabulary which leads to better findability and easier information management. A taxonomy should be agreed upon by business and content owners, and flexible enough to respond to changing business needs.
Using the Taxonomy Features in AEM Assets
Let’s get nomenclature out of the way. In AEM, taxonomy is referred to as “tagging” or “tags.” And a top-level set of tags is referred to as a “namespace.” These tags can be applied as metadata on an asset or page. In AEM, you can manage tags here: /libs/cq/tagging/gui/content/tags.html/etc/tags
For help on using tags in AEM, see: https://helpx.adobe.com/experience-manager/6-3/sites/authoring/using/tags.html