NoSQL databases, which stand for "Not Only SQL," have emerged as a response to the evolving demands of modern data storage, driven by factors such as the explosion of web data, mobile usage, and analytics. Unlike traditional relational databases, which were designed to minimize data duplication when storage was costly and operate primarily on a single server, NoSQL systems offer flexible, scalable, and distributed solutions capable of handling the vast and varied data formats of today. They support multiple data models like key-value, document, column, time series, and graph, and allow for agile development through schema-free data modeling, typically using JSON. This flexibility enables developers to adapt quickly to changing requirements without the formal schema changes needed in relational databases. NoSQL databases can also operate on basic hardware and scale horizontally by simply adding more servers, which can be more cost-effective and reliable than scaling relational databases vertically. While NoSQL systems are adept at managing semi-structured data and providing always-available services for web and mobile applications, they also incorporate some relational capabilities, such as supporting SQL queries and ACID transactions. These features make NoSQL an attractive option for organizations seeking to deliver exceptional customer experiences, as evidenced by its adoption by companies like Couchbase, which combines NoSQL's flexibility with familiar relational database concepts.