|Google Play:||Check if it's there|
UMS Interface allows you to chose a block device or disk image as a 'disk',and communicate with PC through usb mass storage (just as usb disk do).
There are some special usages. For example, you can select the whole emmc '/dev/block/mmcblk0' and mount it to pc linux, so that you can some tool like gparted to do something like partition. And you can also use it as boot disk.