Okay kiddo, so imagine you're a priest a long long time ago. When you dressed up in your special priestly clothes, you put on a special piece called a breastplate. This breastplate was really important because it had different colors and stones on it that all meant something special.
The breastplate had 12 different stones on it, each one representing one of the 12 tribes or groups of people in the community. And each stone was a different color, so it looked really pretty and colorful!
Now here's where it gets even cooler: the breastplate also had two special stones on it that could light up and help the priest to ask God for answers to important questions. These stones were called the "Urim" and "Thummim". When the priest prayed, he could ask God a question, and if the stones lit up, he knew that God was saying "yes" or "no".
So basically, the priestly breastplate was a special piece of clothing that helped the priest to connect with God and communicate with him. It was super important to the community and was considered a really big deal.