Metadata is “data that provides information about other data”. Two types of metadata exist: structural metadata and descriptive metadata. Structural metadata is data about the containers of data. Descriptive metadata uses individual instances of application data or the data content.
Metadata was traditionally used in the card catalogs of libraries. As information has become increasingly digital, metadata is also used to describe digital data using metadata standards specific to a particular discipline. Describing the contents and context of data or data files increases its usefulness. For example, a web page may include metadata specifying what language the page is written in, what tools were used to create it, and where to find more information about the subject; this metadata can automatically improve the reader’s experience.
A main purpose of metadata is to facilitate in the discovery of relevant information, more often classified as resource discovery. Metadata also helps organize electronic resources, provide digital identification, and helps support archiving and preservation of the resource. Metadata assists in resource discovery by “allowing resources to be found by relevant criteria, identifying resources, bringing similar resources together, distinguishing dissimilar resources, and giving location information.”