What exactly is lost by flashing the FS?

[Nazgulled]

Firmware has two parts:
1. FS: It contains languages, images, sounds, animations, settings, etc. Anything that isn't pure software.
2. Main: It contains the software.

Nice day

So, you're saying that when I flash the FS (forget the MAIN for now) I'll loose any language, images, sounds, animations and settings I've changed and installed? I also would like to know what that "etc" means, I want to know what to backup before flashing the FS just so I don't loose my stuff.

But the stuff that we will lost flashing the FS is just the files that are stored in the phone's internal memory only right?

@mohdumer
I didn't ask any of that... :S