A good starting point for finding out more about MongoDB is MongoDB - Wikipedia, the free encyclopedia but in summary it is an open source, "NoSQL" database that works with JSON documents, although it is developed by a company who provide commercial editions.
The first thing to note is that MongoDB is a database server and runs in a process, like MySQL, Oracle and SQL Server and is not file based like SQLite. I believe a command line interface comes as standard, however a GUI tool like Robomongo — native MongoDB management tool (Admin UI) is well worth considering.