HBase is designed based on a Google white paper, Big Table: A Distributed Storage System for Structured Data and defined as a sparse, distributed, persistent multidimensional sorted map. HBase is a columnar and partition oriented database, but is stored in key value pair of data. I know it's confusing and tricky, so let's look at the terms again in detail.
Sparse: HBase is columnar and partition oriented. Usually, a record may have many columns and many of them may have null data, or the values may be repeated. HBase can efficiently and effectively save the space in sparse data.
Distributed: Data is stored in multiple nodes, scattered across the cluster.
Persistent: Data is written and saved in the cluster.
Multidimensional: A row can have multiple versions or timestamps of values.
Map: Key-Value Pair links the data structure to store the data.
Sorted: The Key in the structure is stored in a sorted order for faster read and write optimization.