MongoDB is an open-source, document based  NO-SQL database.

Before learning the MongoDB it is better to understand different MongoDB terminologies.

NoSQL databases ("not only SQL") are non-tabular databases that store data differently than relational tables.

What is No-SQL?

These are a kind of non-relational database that are designed to store and query data as JSON-like documents.

What is a document-based database?

MongoDB stores data records as BSON documents.BSON is similar to JSON

Document in MongoDB?

MongoDB saves Mongo collections in Mongo databases.

Databases in MongoDB

Is a group of documents. Mongo collection is similar to Table in SQL relational database.

Collection in MongoDB?

Is a fully-managed cloud database.MongoDB Atlas is the best way to deploy, run, and scale MongoDB in the cloud.

Altas in MongoDB