I've read through documentation and it seems they just stop before they state exactly what the seL4 kernel does.

So what I'd like to know is what features and components are in the kernel and what is outside of it?

Does the kernel have a single kernel stack or multiple kernel stacks and is/are it/they in kernel mode or user mode? 

Are there any good diagrams that show how seL4 works with its user space components?

Thanks in advance