Metadata is data that describes other data. The term refers to any file or database that holds information about another file or database’s structure, attributes, processing or changes.
Their main purpose is to facilitate in the discovery of relevant information, more often classified as resource discovery. This enables the basic characteristics of a file or database to be recognised and understood without needing to analyse the entire data set.
Metadata also helps organise electronic resources, provide digital identification, and helps support archiving and preservation of the resource.
Metadata is traditionally in the card catalogues of libraries. As information has become increasingly digital, they are also used to describe digital data using standards specific to a particular discipline.
By describing the contents and context of data files, the usefulness of the original data/files is greatly increased. Structural metadata is about the design and specification of data structures and is more properly called “data about the containers of data”; descriptive metadata, on the other hand, is about individual instances of application data, the data content.
Metafiles are commonly used in the header of web pages to deliver instructions to browsers, search engine robots and so forth. The title and description metatags help Google decide what the page is about, the language metatag tells the outside world what language is in use and so forth. Metadata on video files can notify the video player what resolution to display with, what player size to generate and what to display as an opening screen.