Metadata is a set of data that describes and gives information about other data.
For instance, the card catalogue in a public library is a collection of metadata. In the case of the card catalogue, the metadata are the information stored on the cards about the Author, Title, and Publication Date of the book or resource (recording, etc.) in question.
The value of metadata lies in its ability to more efficiently classify and organize information, as well as to yield deeper insight into the actions taking place across the resources, providing more intelligence and higher quality information to fuel big data initiatives, automation, compliance, data sharing, collaboration and more.