Episcopal polity is a way of organizing a church. It's like having a set of rules and leaders who make decisions for the church.
In an episcopal polity, the church has bishops who are like bosses, but they don't have the same power as a king or queen. They work with other church leaders and make decisions together.
The bishops help to guide and support the other leaders and members of the church. They also make sure that everyone follows the rules of the church and does what is best for the church.
Think of it like playing a game with your friends. Someone has to be the leader who makes the rules and helps everybody else. That's what bishops do in an episcopal polity.