Okay kiddo, so you know how we use computers and they run really fast? Well, the iron law of processor performance says that there are three things that affect how fast a computer can be: the number of instructions, how long it takes to do each instruction, and the frequency at which the computer can do those instructions.
Think of instructions like tasks you give your computer to do. Some tasks are really simple, like adding two numbers together, and some tasks are more complicated, like searching through all the files on your computer to find a specific word. So the more tasks you give your computer, the longer it will take to do all of them.
Now, every task also takes a certain amount of time to complete. Some tasks can be done really quickly, like adding two numbers together, and some tasks take longer, like editing a big video file. The longer each task takes, the longer it will take for the computer to finish everything.
Finally, the frequency is how many times per second the computer can do those tasks. Think of it like how many times you can blink your eyes in a second. Some people can blink really fast, like ten times a second, and some people blink slower, maybe five times a second. The same goes for computers - some can do lots of tasks really quickly, while others can only do a few at a time.
So, to sum it up, the iron law of processor performance says that the more tasks you give a computer, the longer it will take to do them, and the faster the computer can do those tasks, the faster it will be overall.