MongoDB is an open-source document database that provides high performance, high availability, and automatic scaling. In simple words, you can say that - Mongo DB is a document-oriented database. It is an open source product, developed and supported by a company named 10gen. MongoDB is available under General Public license for free, and it is also available under Commercial license from the manufacturer. The manufacturing company 10gen has defined MongoDB as: "MongoDB is a scalable, open source, high performance, document-oriented database." - 10gen MongoDB was designed to work with commodity servers. Now it is used by the company of all sizes, across all industry.