Based on Google's Bigtable, HBase "is an open-source, distributed, version, column-oriented store" that sits on top of HDFS. A super scalable key-value store. It works very much like a persistent hash-map (for python developers think like a Dictionary). It is not a conventional relational database. It is a distributed, column oriented database. HBase uses HDFS for it's underlying. Supports both batch-style computations using Map Reduce and point queries for random reads