Mission sui iuris

"Mission sui iuris" means "self-governing mission" in Latin. It's like a group of people who are trying to spread their religion to other places. They have their own leaders and they make their own decisions about what to do. Just like when a group of kids plays a game and they decide how to play and give each other jobs. But unlike a group of kids, a mission sui iuris can be made up of grown-up people who are very serious about their religion. They try to teach and help people who want to learn about their religion in other places. And when they are not sure what to do, they can ask for help from bigger religious groups.