The MongoDB data bases on the JSON (Java Script Object Notation) format. JSON allows for the transfer of data
between web applications and servers using a human readable format.
Before JSON, XML was used for this.
JSON is defined in MongoDB’s BSON (Binary JSON). The binary format of BSON provides reliability and greater efficiency when it comes to speed and storage space.
JSON & BSON
JSON can only represent a subset of the types supported by BSON.
For More Details about JSON Click Here and BSON Click Here