Metadata are data that provide information about other data, generally a dataset. These data, in combination with documentation, help you, your colleagues, and computers to comprehend the meaning behind the data in the datasets. 

Metadata also enables interoperability (i.e. the ability to exchange data and interpret that data) since they provide a clear definition of the data that can be used to interpret them. Most metadata in medical datasets are added using ontologies. For more information see our blog article: Metadata: what are they and why do I need them?