Confraternity of Christian Doctrine. (Yes, I googled. Like I'm going to remember after all these years. lol) I was baptized Catholic when I was one day old and then again when I was a little older, so I've always been Catholic. My mom, grandma and great grandma have also always been Catholic. In my area, it's for good little catholic children who don't go to catholic school, but still need to get in God's good graces and learn about the fires of hell and all that. lol BUT, I bet none of you have ever told a nun that your dad is a prostitute.
It is used for converts, but also for young children. It's apparently VITAL for children. lol Here's what Wiki via Google says.
"CCD attendance is considered by the Holy See to be vital to children's development as Catholics. These classes not only educate children about Jesus and the Catholic faith but prepare children to receive the sacraments of Penance (confession), the Eucharist (Holy Communion), and Confirmation."