MongoDB is a document-oriented NoSQL database that stores data in flexible, JSON-like documents called BSON (Binary JSON). Key features include:

• Document-based storage: Data is stored in documents rather than rows and columns
• Schema flexibility: Documents in a collection can have different structures
• Horizontal scalability: Built-in support for sharding across multiple servers
• Rich query language: Supports complex queries, indexing, and aggregation
• High availability: Replica sets provide automatic failover
• GridFS: For storing large files
• ACID transactions: Support for multi-document transactions