The Church of Jesus Christ of Latter-day Saints
Young people are encouraged to go on missions when they get old enough. Men may go for two years after they are 18 years old (as long as they have graduated from high school), and women may go for 18 months after they are 19 years old. Before an August 2012 change in church policy, men had to be 19 in most countries, and women throughout the world 21, before they could go on missions. More men go on missions than women do. These missionaries go to a "Missionary Training Center" for a few months where they learn how to be good missionaries, and then live in another place for their mission. The Church tells them where they need to go. Then they work with one other missionary who is the same gender as they are (called a "companion"), and change companions often so they are not always with the same person. Missionaries will go to people who live near them and teach them about the Church, and baptize people who want to join the Church. They also help people around them, even if these people are not in the Church. Often they help by building houses for people who need them.