Data that describes an e-book, such as the author, title, or subject.

The word metadata means 'data that describes other data'.

Adding metadata to an e-book file makes it easier for computers to search and index the file.

Metadata is necessary because computers do not understand context. Whereas a human being can look at a book cover and pick out the author's name, whether it comes before or after the title, a computer needs each piece of information to be specifically marked.

Metadata in EPUB files is encoded using the Dublin Core metadata terms.