Apple released most of its round of mid-stream features updates today, including iOS 11.3, watchOS 4.3, and tvOS 11.3, which have been in beta since late January. The one thing that's notably missing is macOS 10.13.4 High Sierra, although that will likely arrive later this week.
If it's not entirely obvious, iOS 11.3 is the most significant of the bunch, containing the most features. Most notably, you'll now be able to check the health of your iPhone's battery, and you'll be able to see if your device is being throttled because of it.
iPhone X users will see new Animoji, including a lion, bear, dragon, and skull. Messages now includes a Business Chat feature that allows you to connect to representatives from businesses, and you'll find this in watchOS 4.3 as well. Also, the new Health Records will allow you to view all of your medical records in one place.
As for watchOS 4.3, there's not a lot that's new there. It's mainly just made up of features that coincide with iOS 11.3, such as the Business Chat mentioned above.
tvOS 11.3 also includes a few minor improvements, including enhancements to Match Content, automatic frame rate switching on the fourth-generation Apple TV, and automatic mode switching for AirPlay.
Update: An earlier version of this article said that Messages in iCloud is included in iOS 11.3; however, it has been removed from the final build.