MongoDB uses a document-based data model. Each piece of data (equivalent to a row in a traditional database) is called a document, built and stored in a JSON-like format. Because of its JSON-based structure, MongoDB can store documents within fields, naturally forming a directory-like, multi-level structure known as a sub-structure. MongoDB also has built-in support for multi-value fields, allowing arrays to be stored directly in a field without the need for a separate table. Array fields are fully controllable by users. You can build indexes on them, search and update individual elements within an array, and dynamically add or remove any element.

Document databases are both natural and flexible for developers, enabling higher productivity and faster development based on application needs. As a NoSQL database, the document data model has become a popular alternative to relational databases.