To try to explain Cursillo to someone who has never experienced Cursillo is at best, difficult. Often, for those who have experienced Cursillo it is still somewhat mystifying. This is not because the Cursillo Movement is a "secret" organization. The reason behind the mystery is God. No one can fully explain how God touches each person in His special/unique way throughout the various elements of the Cursillo Movement
What is Cursillo?
"The Cursillo Movement is both a movement and a method. The purpose of the movement is to create small groups of Christians that will evangelize their environments with the gospel spirit. The purpose of the method is to help persons live what is fundamental for being a Christian by committing themselves to the spiritual aids the church offers in order to grow in holiness, formation and evangelization".-- "The Pilgrim's Guide"
For more information, see the frequently asked questions (FAQ) about Cursillo