MongoDB is a popular open-source, NoSQL database designed to store and manage large volumes of unstructured or semi-structured data. Unlike traditional relational databases, MongoDB uses a flexible, document-oriented data model where data is stored in JSON-like documents (called BSON – Binary JSON). This allows developers to store complex, hierarchical data in a single record, making it ideal for applications that require fast development and scalability. MongoDB supports dynamic schemas, meaning you can change the structure of documents without affecting the rest of the database. It is highly scalable, both vertically and horizontally, and supports features like replication for high availability and sharding for distributed data across multiple machines. It integrates well with modern programming languages such as Java, Python, and Node.js, and is widely used in big data, real-time analytics, content management systems, and IoT applications. Thanks to its performance, flexibility, and ease of use, MongoDB is a preferred choice for developers building modern, data-intensive web and mobile applications.