Java Runtime Engine (JRE) is required for PolyBase installations. SQL Server PolyBase is the technology that allows data integration from other sources other than SQL Server tables. PolyBase is used to access data stored in Hadoop File System (HFS) or Windows Azure Storage Blob (WASB).
As you will see later in this book, SSIS can now interact with these types of storage natively but having PolyBase handy can save us valuable time in our ETL.