You might not know it, but inside your Intel system, you have an operating system running in addition to your main OS, MINIX.
MINIX is running on “Ring -3” (that’s “negative 3”) on its own CPU. A CPU that you, the user/owner of the machine, have no access to. The lowest “Ring” you have any real access to is “Ring 0,” which is where the kernel of your OS (the one that you actually chose to use, such as Linux) resides. Most user applications take place in “Ring 3” (without the negative).