What are the /firmware and /efs partitions on Samsung devices This is specifically the Galaxy s3.  Out of curiosity what are these partitions exactly.  Are they part of the android OS or something lower level than that? If I were to delete everything in these partitions will I brick the phone even after a complete factory restore from "Download mode"? If these are not in fact android partitions why do some ROMs flash them?  What is the difference between /firmware and /efs and are these flashed with most ROMS?

I've been googling the partition structure of my device and these things are not clear. Please help me clear them up :)
According to this linky here this is what it has to say


  What is EFS? It is a place that stores your Android smartphone
  important data like Wi-Fi, Bluetooth MAC address and IMEI
  (nv_data.bin).


After reading the above linky, it would be prudent to make a backup of that partition otherwise well and truly hosed! :)

As for /firmware I am guessing that is where the original stock firmware goes into when updating via the official route a lá Kies. 

If anyone has a better insight feel free to comment, and I will gladly amend this accordingly :)