Apache HBase is an open-source, distributed, NoSQL database built on top of the Hadoop ecosystem. It is designed to handle large amounts of sparse data across clusters of commodity hardware. HBase provides real-time read and write access to large datasets and is modeled after Google's Bigtable. It is particularly well-suited for use cases that require random, real-time access to big data, such as online applications and analytics. HBase supports horizontal scalability, fault tolerance, and automatic sharding, making it a popular choice for big data applications.