Metadata is a structured and standardized subset of data, often described as ‘data about data’. They contain, among other, administrative information about the data (Title, author, language, format, date, embargo period, editor, license, access conditions, etc.) Metadata is used by repositories and browser to catalog data and further facilitate data finding and reuse. Metadata also serve as a bibliographic record for citation
There are international standards for metadata (DublinCore, DataCite Metadata Schema). However, metadata may depend on the repository and/or discipline. If you want further information on your research community standard of metadata, look at the catalogue of disciplinary metadata standards http://www.dcc.ac.uk/resources/metadata-standards
(this information contributes to the “F”, and “A” of FAIR data management)