Metadata is structured information that makes it easier to find, use, and manage information. Metadata is often referred to as data about data. Decisions about metadata should be made early in the data management process.
There are three kinds of metadata:
Descriptive metadata consist of information about the content and context of your data. It may include elements such as title, creator, subject keywords, and description (abstract).
Structural metadata describe the physical structure of compound data. For example, structural metadata for an image may include: camera used, aperture, exposure, file format, and series of images it belongs to, if any.
Administrative metadata are information used to manage your data. This metadata may include when and how it was created, who can access it, software required to use it, and copyright permissions.