Confusing in Address

[hz hanks]

Hi, all

I'm confused with different addresses in Linux, such as virtual
address and hardware address. For example, which kind of address one
can get when using "&num" in application layer programming? How about
that in kernel, such as in device driver? Which kind of address one
can get when using "void _ _user *to" in device driver? And which kind
of address the kernel is working with when using "mmap"? And which
kind of address we are talking about when divide the memory into user
space and kernel space?

It's quite tedious but thank you so much for helping me!