Explain Taxonomy in drupal .

Drupal has a system for classifying content, which is known as taxonomy and implemented in the core Taxonomy module. You can define your own vocabularies (groups of taxonomy terms), and add terms to each vocabulary. Vocabularies can be flat or hierarchical, can allow single or multiple selection, and can also be “free tagging” (meaning that when creating or editing content, you can add new terms on the fly). Each vocabulary can then be attached to one or more content types, and in this way, nodes on your site can be grouped into categories, tagged, or classified in any way you choose.