Metadata is 'data about data'. Put another way, it is the information necessary to make your data 'independently understandable'. Using established metadata standards will help make your data discoverable, citable, and ready-to-use by others.
Metadata standards or schemas consist of specific elements used to describe or document your data. Many disciplines have established metadata standards. Some data repositories have their own standards. One of the standards listed below might be exactly what you need to document your data. If there is not a standard already in place for your data, there are several general purpose schemas that you can adapt to your needs. Your Subject Liaison Librarian will be familiar with the metadata standards used in your discipline.
Metadata Concept Map by Amanda Tarbet is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.