The AWS Glue Data Catalog is used as a central repository that is used to store structural and operational metadata for all the data assets of the user. E.g. for a given data set, user can store its table definition, the physical location, add relevant attributes, also track how the data has changed over time. The AWS Glue Data Catalog is like a Apache Hive Metastore that is compatible and is a drop-in replacement used for the Apache Hive Metastore in Big Data applications that is running on Amazon EMR.