why is metadata used
Metadata is data that describes other data. Meta is a prefix that in most information technology usages means an underlying definition or description.. Metadata summarizes basic information about data, which can make finding and working with particular instances of data easier.
1 Descriptive Metadata: Metadata that describes the intellectual content of a resource and used for the indexing, discovery and identification of a digital resource.  Administrative Metadata: Metadata that includes management information about the digital resource, such as ownership and rights management.