ELI5: Explain Like I'm 5

processor microcode

Processor microcode is like instructions for a computer chip. It tells the chip what to do and how to do it. It's like a set of instructions for the chip, like a recipe that tells it how to work. The microcode tells the chip what to do when it receives certain types of information, like how to add two numbers together. Without microcode, the chip wouldn't be able to understand what it's supposed to do.