Briefly explain Document Database

Answer:

The word document in document databases connotes loosely structured sets of key/
value pairs in documents, typically JSON (JavaScript Object Notation), and not documents or spreadsheets (though these could be stored too).
Document databases treat a document as a whole and avoid splitting a document into its constituent name/value pairs. At a collection level, this allows for putting together a diverse set of documents into a single collection. Document databases allow indexing of documents on the basis of not only its primary identifier but also its properties. Document stores are used for large, unstructured or semi-structured records.
Examples : MongoDB,CouchDB etc.