Plated mail is like wearing a suit made of tiny metal pieces called "links" that are connected together. These metal links cover your body and can protect you from swords and arrows in a battle.
Now, sometimes people want even more protection, so they add small metal plates (like tiny little shields) on top of their mail. This makes it even harder for enemies to hurt them.
But wearing plated mail can also make you very heavy and slow, because it is like wearing lots of metal clothes. So sometimes people only wear plated mail on certain parts of their body, like their chest, or arms, where they really need the extra protection.
Overall, plated mail is a special type of protective clothing made of metal links and sometimes metal plates, that can help people stay safe in battle.