MongoDB is a open source document storage system and leading NoSQL & Un-Structured database. MongoDB is written in C++ programming language.

Structure on MongoDB:

 

MongoDB-Server-1.png

Terminologies in MongoDB:

Document
A Document is a set of key-value pairs. Here the keys are not pre-defined format and it will be dynamic.
Document’s are dynamic in nature, documents under the same collection need not be having same set of fields or structure.

Collection:
                  Collection is a group of MongoDB  documents similar to table in RDBMS. Collections doesn’t enforce the schema definition and doesn’t force for typed data too.
Although, Collection’s are considered to be of similar or related purposes.

Ex: data’s from same form in the application.
Create collection‘s for different form, persist data for each form in specific collection

Database:

Here the database is considered as physical container for multiple collections. Each database of MongoDB will have own set of file on File Systems.
It is important to note a single MongoDB can hold multiple database.

 

MongoDB (1)

 

Here few RDBMS terminology comparison between MongoDB and RDBMS.

RDBMS

MongoDB

Database Database
Table Collection
Index Index
Row Document
Column Field
Joining Linking & Embedding
Partition Sharding (Range Partition)
Replication ReplSet