Why Virtual Memory Address is the same in different process?

Question

I know the virtual memory separates 2G(for kernel)/2G(for user) in Windo

Answer 1

That's exactly what virtual memory is. The operating system provides each program with its own private address space. In reality the operating system is in charge of mapping those virtual addresses back to the physical address space without the application being aware.

As you noticed this means that two applications can have different data residing at the same virtual address in the program.

Read more about virtual memory here.