An application communicates with MongoDB by way of a client library, called a driver, that handles all interaction with the database in a language appropriate to the application.
See the following pages for more information about the MongoDB drivers:
Driver version numbers use semantic versioning or “major.minor.patch” versioning system. The first number is the major version, the second the minor version, and the third indicates a patch.
Driver version numbers.
If your driver has a version number of 2.9.1, 2 is the major version, 9 is minor, and 1 is the patch.
The numbering scheme for drivers differs from the scheme for the MongoDB server. For more information on server versioning, see MongoDB Version Numbers.