MongoDB Opensource vs MongoDB Enterprise

It's all explained on the website.

The open source version has no artificial limitations in any of the aspects you mentioned. The advantages of the enterprise version are:

• MongoDB Management Service (backup and monitoring solution)
• SNMP monitoring
• Kerberos or LDAP as an alternative to password-based or certificate-based authentication
• Commercial development license (changes you do to MongoDB itself aren't subject to the terms of the AGPL). Note that in a usual setup you have your clients communicate with your application server and your application server communicate with MongoDB. In that configuration the AGPL does not require you to publish any sourcecode because the end-users do not interact with MongoDB directly over a network. It only matters when you expose MongoDB to your clients directly. And even then compliance with the AGPL is only problematic when you make changes to MongoDB itself.
• MongoDB BI-Connector which adds a limited (very limited) SQL compatibility layer to MongoDB for integration with SQL-based Business Intelligence solutions.
• MongoDB compass - a GUI tool to visualize data structures (but there are free alternatives for that). As of April, 2020 the full version of Compass is now free for everyone.
• In-Memory storage engine (as of version 3.2 still in beta-stage and not yet recommended for production use!)
• Support and training contract
• Encrypted Storage Engine to (optionally) protect data at rest
• Certification for some operating systems (considering that the free edition is identical except for the additional features listed above, paying just for this is quite pointless. But maybe you work in a place with lots of MBAs who care about such formalities)

When you can do without all these things, you don't need to pay for the enterprise version.

I think you are asking if there are any limitations or restrictions in terms of basic functionality between MongoDB Enterprise and the community/OSS version. The answer is no - there is no difference or restriction in terms of the amount of memory, storage or number of instances/sets/clusters you can run using the OSS version, nor is there any difference in the failover mechanics between the two.

The differences (as listed on the MongoDB Enterprise page) are all related to security, authentication/authorization, auditing, monitoring integration, backup, support, licensing etc.

In other words, the differences are all in areas most likely to be attractive to businesses/enterprises looking to run the MongoDB database as a critical, integrated system in a responsible, supported way.

Well, Just to be more sure I called the MongoDB Customer Support Team.There are three different version of MongoDB as per now.

1. Community Server
2. Professional
3. Enterprise

Actually Community server is free and other 2 are paid software.

I asked the guy-

Where can I use Community Server of mongodb?

Below the response I received through Email-

Community Server's Suggested use is for development environment. For production purpose Enterprise offering is required.

Please be sure before using the version.