Here’s the changelog. As you can see, it’s highly descriptive.
- Android KitKat 4.4.4
- Miscellaneous improvements, bug fixes, and security updates
You can head into the update menu to manually pull the OTA, otherwise it will show up in a few days.
[Not Lollipop] Samsung Galaxy S5 Active On AT&T Gets An Update To Android 4.4.4 was written by the awesome team at Android Police.