Okay, imagine you have a secret treasure box and you're the only one who knows the secret code to open it. The power of the keys is like having the secret code or password to something important.
In some religions, there are leaders called bishops or priests who are given the power of the keys. This means they have been trusted with the secret codes (like a password) to help people do really important things, like make peace with God or forgive someone for something they did wrong.
Just like you wouldn't give the secret code for your treasure box to just anyone, only certain leaders are given the power of the keys because they are trusted and responsible. They use this power to help people in difficult times and bring them closer to God.