1. HCatalog is a table and storage management layer for Hadoop that provides a relational view of data in HDFS and abstracts data formats and locations from users. 2. Previously, HAWQ accessed Hive tables through PXF using external tables, but this required specifying the schema, location, and format which was error prone and wouldn't detect metadata changes. 3. The new integration retrieves metadata from HCatalog and parses it into in-memory catalog tables to provide dynamic access to Hive tables from HAWQ without needing to specify schemas.