In short, it is a custom programmer file that commands your computer to communicate directly with the phone's flash storage, completely bypassing the broken Android operating system, recovery partition, and fastboot interface. Why and When Do You Need It?
Click on Browse next to the "Programmer Path" field. Navigate to your extracted stock firmware folder and select prog-emmc-firehose-8953-ddr.mbn . Prog-emmc-firehose-8953-ddr.mbn
Error: "Firehose Handshake Failed" or "Device Rejected Programmer" In short, it is a custom programmer file