Extra-low voltage (ELV) is like a special kind of electricity that is very, very safe. Imagine you have a toy car that needs batteries to work. The batteries you put in the toy car are like extra-low voltage. They don't give off a lot of power, so they won't hurt you if you touch them.
In fact, extra-low voltage is so safe that you can touch it with your hands and it won't hurt you at all. But just because it's safe doesn't mean it's not useful. Extra-low voltage is used in things like phones, computers, and other electronics that you use every day.
So next time you see or hear about extra-low voltage, you can remember that it's like the small batteries in your toy car that are safe to touch, but very useful for powering important things.