In HBase, tables are split into smaller chunks that are distributed across multiple servers. These smaller chunks are called regions and the servers that host regions are called RegionServers. The master process handles the distribution of regions among RegionServers, and each RegionServer typically hosts multiple regions. In HBase implementation, the HRegionServer and HRegion classes represent the region server and the region, respectively. HRegionServer contains the set of HRegion instances available to the client and handles two types of files for data storage:
HLog (the write-ahead log file, also known as WAL)
HFile (the real data storage file)
In HBase, there is a system-defined catalog table called hbase:meta that keeps the list of all the regions for user-defined tables.