That's not true. If your MacBook is a model sold as brand new in 2012, it can go all the way up to the latest OS X available (which is El Capitan 10.11). And in a about one week, it can even run the newest "macOS" Sierra, which is supposed to be released 9/20.
You need to run Mac App Store and download the installer for later releases of OS X. It won't update automatically. If Snow Leopard is the current OS X release installed, the latest version of Snow Leopard is 10.6.8. But Snow Leopard is not the latest release your MacBook can run.
Check out the link I provided in my previous reply, about upgrading to El Capitan.
NOTE: Upgrading your OS may make some third-party apps you use incompatible. You should make a backup before a major OS upgrade. You can use the built-in Time Machine feature to automate backups to an external drive, if you do not already.