Checkout Ivan’s article of the same name: Ivan Mironchuk: Taxonomy vs. Metadata. Here’s a few excerpts:
What is Metadata?
Metadata is data about data! Think of metadata as information about an asset beyond the basic filename. Any sort of attribute or element that helps to define or describe a particular image, document, presentation or spreadsheet would be considered metadata.
What is Taxonomy?
Taxonomy (from Greek “taxis” meaning arrangement or division and “nomos” meaning law) is the science of classification according to a pre-determined system with the resulting catalog used to provide a conceptual framework for discussion, analysis, or information retrieval.
Checkout Ivan’s article for his additional thoughts.