I am a normal man-in-the-street computer user and so do not really understand what this is about, but I want to. Can someone please explain to me if:

1. The Windows 8/UEFI secure boot thing will make it impossible to run normal/legacy applications in Windows 8 (as they will be unsigned)?
2. It will turn Windows into an Apple-like system where only Microsoft approved applications can be run?

As I say, I'm a normal user, and that is the overall impression I have from reading all the blogs, etc about it.

If, on the other hand, all it does is make sure the system is booting a signed OS, how does this prevent malware (which is what at least two Microsoft blogs that I read seemed to be saying), given that most malware is not part of the boot process? The only way I can see this making sense is if it is ensuring that all OS components are signed. Is that it?

Like I say, I'm a mortal, so please don't get technical on me, but rather explain how it will affect me, the user.