The document discusses HBase, an open-source, non-relational, distributed database modeled after Google's Bigtable. It outlines some limitations of relational databases that HBase addresses like scaling to large datasets and high write throughput. Key aspects of HBase covered include its column-oriented design, data model organized by row keys and column families, and architecture involving a master node, Zookeeper, and region servers. Common uses of HBase and how its schema differs from relational databases are also summarized.