HBase is a column-oriented database management system that runs on the HDFS and is typically used to distribute data sets.
HBase does not support a structured query language such as SQL, as opposed to relational database managers.
The system provides a layer on HDFS that provides good performance for analytics in streaming, was created precisely to meet that need.
Having a processing engine in memory greatly speeds up read-write operations on Hadoop, allowing you to work with real-time data.
Access can be made from Hive, Pig and MapReduce and uses HDFS to store the information, so it is fault tolerant.
Source: Official website