MongoDB is a scalable, high-performance, open source, document-oriented database. It supports a large number of languages and application development platforms.
MongoDB is a widely used, general-purpose, document-oriented NoSQL database with features including high-availability replication and auto-sharding for horizontal scaling. The MongoDB database server and tools, written in C++, are open-sourced and available under AGPL v3.0 license or a Commercial License. MongoDB has strong support for dynamic querying and aggregating data including MapReduce and an Aggregation Framework. MongoDB uses BSON (Binary JSON) format for storage purposes and the MongoDB Wire Protocol for communication between client drivers and the MongoDB server. Officially supported Drivers and Client Libraries are available for most popular programming languages, and there are also Community Supported Drivers which offer alternative implementations and support for further programming languages.
adapted from Stack Overflow SE.