Think of it as data about data. The prefix 'meta' means 'among', or 'together with'. Metadata may be a part of the resource itself, or be kept separately from it. Imagine looking for a book at a library with no catalogue. The main reason for metadata is to improve the management and retrieval of information.
Good metadata can improve the efficiency of searching for something specific.
If we know the book's author, the search becomes easier. If we also know the publisher, the task becomes easier again. The wider the scope of the metadata, the narrower our search becomes. One of the most important steps in the development of the Web beyond a chaotic repository of information, is our ability to bring some order to its contents. The way we search for information on the Web is by using one of the search engines like Yahoo, Lycos or Alta Vista and typing in our search request in the form of a word or phrase.