iOS 8.4.1 Beta is a minor update compared to iOS 8.4, since it only features bug fixes, performance enhancements, as well as minor tweaks to the system. However, the company could be looking to patch exploits used by PP Jailbreak and TaiG Jailbreak, or just fixing some issues with Apple's long-awaited and much anticipated music streaming service, Apple Music.
iOS 8.4.1 is now available through Software Update or via the iOS Dev Center for registered devs.