MongoDB is an open-source, document-oriented NoSQL database designed for efficient data storage and handling large volumes of structured or unstructured data. It differentiates from traditional RDBMS by having a dynamic schema, faster performance, and a BSON format for documents, but has limitations like high memory usage and restrictions on document size and nesting. The document introduces usage scenarios, pros and cons, and integration with Spring Boot through MongoRepository for building CRUD applications.