Why there are various setup variables in NVRAM?

I’m having some issues with my PC and I discovered my system has more than one setup variable, but I don’t know what the other one is used for. One of these setup variables contains a binary blob with BIOS configuration, which can be restored to default pulling off CMOS battery.
Is the second setup variable used to tell the first one what default options to get from BIOS or does it contains BIOS settings too (as the first one)?
Can I delete the second setup variable or is it necessary for the PC to run?
If they are different, how can I know who is who?