The "fg" in the filename stands for , the pseudonym of one of the internet’s most famous "repackers." Repacks are versions of video games that have been heavily compressed to make downloading easier for those with slow internet or data caps.
By making the soundtrack optional, the repacker can shave several hundred megabytes—or even gigabytes—off the total download size for users who only care about playing the game. How to Use the File fg-optional-soundtrack.bin
The Mystery of "fg-optional-soundtrack.bin": Everything You Need to Know The "fg" in the filename stands for ,