So, a protodeacon is like the helper of the church leader called the bishop. They help the bishop during important church services and ceremonies.
It's kind of like how you might help your parents when they are doing something important, like cooking a big meal or throwing a party. The protodeacon helps the bishop with things like carrying important items called "holy vessels" during the service, making sure things are set up properly, and organizing the other helpers.
Sometimes, if the bishop is absent, the protodeacon can even lead the church service! It's a really special role to have in the church community.