FIHSW

FIHSW, stands for the firmware developed by FIH Mobile. Since HMD Global started to use HMDSW for labelling the firmwares for devices that not made by FIH Mobile, especially Wingtech, now all of firmwares created by FIH Mobile are now labelled as FIHSW by Hikari Calyx Tech to distinguish between them.

About Nb0
Nb0 (Pronounced as n-b-zero instead of nb-oh) is the default firmware format used by FIH Mobile. It's actually multiple files packed into a proprietary single file.

This format has many cons. Except third party flashing tool like NTool, flashing this firmware into phone requires initializing everytime - which is actually extract what contains to temporarily directory of your system drive. Also, it's unfriendly to users who just want to extract one single partition image (e.g. boot.img) for special purposes.

A valid Nb0 file has these files packed: all of fastboot images, FTM stuff, checksum files and a flashing script to allow the flashing tool to flash as order.

FIHSW firmware packages naming scheme by HCT
FIHSW_[FIH_Firmware_Build_Version]_[SKUID]_[Android_OS_Version]_[Android_Security_Patch_Level].full.[compress_method].[sha256_checksum].[extensionname]

Explanation:
FIH_Firmware_Build_Version: The firmware build version used by FIH Mobile. See FIH Firmware Build.

SKUID: Default SKUID used for this firmware. For more details, see SKUID.

Android_OS_Version: Which Android OS version is included with this build. For Android 8.x or older, it's shown just like 8.1.0 or 7.1.1. For Android 9, it's only shown as 9 or 10.

Android_Security_Patch_Level: Which Android OS version is included with this build, and the format is YYYYMMDD, e.g. 20180905.

compress_method: How the package is compressed, currently all of sorted FIHSW firmwares use LZMA2 compress method.

sha256_checksum: The SHA-256 checksum, safe and mainstream checksum method, but the con is it will make the filename really long.

extensionname: The package format, currently all of sorted FIHSW firmwares use 7z.