Apple has released the second beta version of iOS 10 to developers. The update can be found on Apple's Developer Download site, or downloaded over-the-air on a phone running the previous beta release.
Apple intends to launch iOS 10 to the public this fall. The update will bring a number of new features and changes to the iPhone and iPad user experiences, including a new lock screen with richer notifications, Siri support for third-party apps, and major updates for Messages.
Apple occasionally offers updates to iOS 10, watchOS 3, tvOS 10, and macOS Sierra as closed developer previews or public betas for iPhone, iPad, and Mac. (Sadly, no public betas for the Apple Watch or tvOS.) While the betas contain new features, they also contain pre-release bugs that can prevent the normal use of your iPhone, iPad, Apple Watch, Apple TV, or Mac, and are not intended for everyday use on a primary device. That's why we strongly recommend staying away from developer previews unless you need them for software development, and using the public betas with caution. If you depend on your devices, wait for the final release.