MongoDB, or simply Mongo, is a popular open-source document-oriented NoSQL database. It is designed to handle large volumes of unstructured or semi-structured data, making it ideal for use in applications that require high scalability and flexibility. Mongo uses a JSON-like format to store data, allowing for easy integration with modern web development frameworks. Its features include automatic sharding, data replication, and a rich query language, making it a versatile and powerful database solution for a wide range of applications.