Apple has released the iOS 10.3.3 software update for iPhone, iPad, and iPod touch.
The release notes don't really tell us much:
iOS 10.3.3 includes bug fixes and improves the security of your iPhone or iPad.
This could very well be the last iOS 10 update before iOS 11 is released in September (barring any major bugs or gaping security holes that emerge), and it could be the last update that the iPhone 5, iPhone 5c, and iPad 4 receive before being made end-of-life by the release of iOS 11.
The iOS 10.3.3 update appears to be an "under-the-hood" update, with no changes made to the user interface.
The iOS 10.3.3 update is an be downloaded over the air (go to Settings > General > Software Update) or through iTunes for all iOS 10.3 users.