MongoDB is an open-source document-oriented NoSQL database used for high volume data storage. It is used to store and retrieve data in the form of documents, which are composed of key-value pairs. MongoDB is designed to provide high performance, high availability, and automatic scaling.
For example, MongoDB can be used to store and retrieve data for a social media application. The application may store user profiles, posts, comments, and other types of data. MongoDB can store this data in a flexible, schema-less way, allowing the application to quickly retrieve and update data without having to define a schema beforehand.