Well, the kernel is not “just a program” in that it is not like the other programs on your system. If it was, you would “just” run it in your shell. The kernel cannot run this way of course because it is not a user mode program.

That said, if course the kernel is a program in the sense that it is a set of machine instructions that make the hardware do what you want.

And the kernel is designed to talk to hardware and other programs—to be the bridge between the two. It is not something an end-user interacts with directly.