Normally we see Apple release iOS and watchOS updates together, but today only watchOS is getting a new update.
watchOS 6.1.3 is now available for download over the air. You can get it by launching the Watch app on your iPhone and selecting "General" followed by "Software Update".
Apple says that this watchOS update includes improvements of bug fixes. One specific bug that's being fixed is an issue that prevents the irregular heart rhythm notification from working as expected for Apple Watch owners in Iceland.
It's always good to have the latest updates available for your devices to ensure that you've got the newest improvements and bug fixes that you can get. So if you've got an Apple Watch, go grab this watchOS update as soon as you can!