The keys of the kingdom is a religious concept that comes from the Bible. It's like a special code or a magical key that gives someone the power to do important things in the church.
Imagine you have a secret password that only lets you into a special room that has all the important papers and things you need to do your job. The keys of the kingdom are sort of like that, but instead of a physical room it's like a spiritual secret that only certain people are allowed to know.
In the Bible, Jesus gives the keys of the kingdom to Peter, one of his disciples, and tells him that whatever he "binds on earth will be bound in heaven, and whatever he looses on earth will be loosed in heaven." This means that Peter has special authority to make important decisions and actions that are recognized by God.
So basically, the keys of the kingdom are like a special tool that gives someone important powers and authority within a church.