This was answered back when this whole nasty thing reared it's head.
If you want to understand the throttling, then you need to understand lithium ion batteries.
As these batteries get old, they lose some of their charge and become unstable. If you try to draw too much power from the battery, the battery freaks out and you do not get a steady stream of power.
RAM
Your memory requires power to hold objects in memory, as soon as a power loss occurs objects start fading out of, or become corrupt in memory. Objects in memory are fed into the processor.
CPU
Your processor is trying to do stuff when this happens, as it's reading bits, it loses power, and it's about the equivalent of someone closing a book you are reading without leaving a bookmark where you left off. If your processor was lucky enough to not get affected by power loss, but the memory was, then as soon as it reads corrupt or missing data, it panics and crashes whatever it was doing.
Other things that could be affected are
- Camera
- GPS
- Wifi
- Cellular
- Bluetooth
- Screen
There are two ways to fix this, either tell your customers to upgrade after a couple of years, or cap the performance of the device so you can improve reliability of the battery and integrity of user's data without forcing users to upgrade.
I'm actually happy with Apple's decision, even if they are applying the throttling to devices with perfectly good batteries, they are doing it to prolong the life of the battery and the device, I'm cool with that. I would rather have a throttled device over an unreliable one. But don't you worry, soon they will allow you to override their precautions so you can test the waters. Just don't come crying back here if your device crashes and you lose or corrupt data when you do some heavy lifting on your phone.