The document discusses NoSQL databases and provides an introduction and comparison of Dynamo, MongoDB and Cassandra. It describes how NoSQL databases are becoming more popular for handling big data as they have a schema-less structure and can scale horizontally. The document outlines some key features of NoSQL databases, including flexible data models, partial record updates, and horizontal scalability. It also categorizes different types of NoSQL databases such as key-value, columnar, and document oriented databases.