https://learn.microsoft.com/en-us/windows/iot/iot-enterprise...
> Unified Write Filter (UWF) is an optional Windows 10 feature that helps to protect your drives by intercepting and redirecting any writes to the drive (app installations, settings changes, saved data) to a virtual overlay. The virtual overlay is a temporary location that is cleared during a reboot or when a guest user logs off.. Increases security and reliability where new apps aren't frequently added. Can be used to reduce wear on solid-state drives and other write-sensitive media. Optimizing Application load timing on boot – it can be faster to resume from a HORM file on every boot rather than reloading the system on each boot. UWF replaces the Windows 7 Enhanced Write Filter (EWF) and the File Based Write Filter (FBWF).