What is the use of the script `sub-bilingual` to generate bilingual subtitles if it needs an already translated subtitle? 

I apologize I can't read the code. so I don't what the intention of it! I was searching for a way to create subtitles using the audio & google got me here. the description says it needs translated subtitles then one must wonder what it is generating? translation has already been done. so what this script is actually doing can you please layman it for me?