My First Thread - SHSH blobs and jailbreaking Questions!!!!! U CAN HELP

I am a newbie and i am confused about shsh blobs...
I want To jailbreak my iphone 3gs to 4.0.1
It is currently running a 3.1.2 and is jail-broken with blackra1n.
In cydia it says "This device has SHSHs on file for iphone OS: 3.1.2, 3.1.3, 4.0, 4.0.1"
Im wondering does this mean i have shsh blobs saved?
If so, if i restore will they go away?
If not, Why is everyone on about saving shsh blobs on their computer with firmware umbrella and if so, How do i put them back on the fone with the shsh on my computer which i have on
my mac.

And my phone has the new bootrom and it was upgraded to 4.0 then downgraded to 3.1.3 then 3.1.2 then restored on 3.1.2 then jailbroken. I don't
know what to do

 

Its baseband 05.13.04 - 6.4_M3S2 by the way