Hmaster, HRegion Server and Region are the main components of HBase.
HmasterHmaster is a master server which is used for monitoring the all region server in cluster. It allocates the regions (table) to the region servers and also handles the load balancing across multiple region server.
HRegion Server HRegion Server is a slave server which is responsible for serving and managing regions. Each Region Server has to serve a set of regions.
Region Region stores the subset of table data. When a table becomes too big, the table is partitioned into multiple Regions.