It's not the latest version of Google's mobile operating system, that's 4.4 KitKat, but Samsung users should be seeing an available update to Android 4.3 Jelly Bean. After bringing the upgrade to the flagship Galaxy S4, Samsung is now rolling it out to the Galaxy S3 and is expected to do the same for the Galaxy Note 2 soon. See Android Advisor.
The Galaxy Note 3 comes pre-loaded with 4.3 and it's unknown why Samsung leap frogged version 4.2 for the S3 and Galaxy Note 2. The firm started internal testing but stopped development, presumably to work on 4.3 instead.
Samsung users updating to 4.3 Jelly Bean will find plenty of changes in terms of the user interface. This includes the tabbed settings menu found on the Galaxy S4, new Samsung keyboard and a new lock screen. It also brings handy features such as actionable notifications, move to SD card feature and better GPU drivers.
If you're interested in buying a smartwatch then you'll be pleased to hear the update add support for Samsung's Galaxy Gear.
As with any firmware upgrade, it will occur in phases in different countries and mobile operators. So if you don't have it yet, be patient and keep checking in the software section of the settings.