What is rootfs ? And if i try flash, what's appenned ?

i have 2 files :
DFL61_HARMATTAN_40.2012.13-7.FRANCEBENELUX_EMMC_FRANCEBENELUX.bin

DFL61_HARMATTAN_40.2012.21-3_PR_LEGACY_001-OEM1-958_ARM.bin

I'm a newbie. sorry...
I have used symbian with my CFW but this nokia...
Coderus, The symbian's God