Couchbase Server is a NoSQL database that allows developers to build applications with agility and scale them to any size. It provides a flexible JSON schema, fast document storage and retrieval using document IDs, and various data access methods like views, global secondary indexes, and the N1QL query language. Couchbase supports many development frameworks and platforms, and can be deployed in various environments including Docker. It provides features like auto-sharding of data across nodes, replication, and cross data center replication for high availability and disaster recovery.