This article discusses software internally used by Apple.
Acquiring a copy without Apple's consent is illegal and may result in being scammed.
USBHost, as the name implies, allows for temporarily converting a device running it from a slave device to a host device. In simpler terms, it lets you (theoretically) use the device as a keyboard, mouse, etc. This is possibly for use with an internal dongle called Ez Dongle (maybe?). For more information, read this wikipedia article. Image 1 is from @ThermalDOE on Twitter.
The contents is as follows on an iPhone 6 running Monarch 13A83262c. The application on this device is fully working and complete.
_internal_usb.png com.apple.osdiags.USBHost.plist Entitlements.plist Info.plist PkgInfo USBHost