Content Classification consists of three primary elements; a Taxonomy, Metadata, and Content Types. Taxonomy is a hierarchical classification of terms. Metadata (Site Column or Field) is “data about data” in that it provides context to content, while a Content Type is a collection of Metadata.
The values in a Metadata field could be populated by Taxonomy terms. It is a common misconception that Taxonomy is comprised of Metadata, when in fact it is comprised of Metadata attributes commonly referred to as terms. These attributes are typically used as values in a Metadata field. Example: A Metadata field is named “Department” where the possible values for the “Department” field from the Taxonomy are “Sales”, “IT” and “HR”. The Content Type is named “Proposal” and includes Metadata fields for “Proposal Title”, “Department” and “Proposal Date”.