A document is basically an entry which is made to a database. Each document has a specific ID, and this unique Id is used to locate the document in the server. The application data like information regarding price and description is stored in the document, and the user can access this application data a per his/her requirement. The document gives the primary information about a particular essential task

On the server not always but mostly the document is stored as a JSON because it is a well-structured format and it can be searched and queried subsequently.

BY Best Interview Question ON 24 Mar 2019