A recent question mentions World Youth Day. Wikipedia says that it's an event for young people organized by the Catholic Church. That isn't very helpful, since there are a lot of different types of Christian youth events. How is World Youth Day different from other events? Why do people go? What can people expect if they go? Who counts as a young person? What's the goal?
I asked the same question to the Priest who lead our (it was my wife and my honeymoon) pilgrimage for the 2005 World Youth Day in Cologne, Germany.
His answer was, It's like a renaissance festival for young(ish) Catholics.
And, since I've never been to a renaissance festival, but I have been to a World Yotuth Day, I think I agree.
Of the few that I've been keen on following up on, in Germany, Australia and Spain, it seems like a major world youth day event takes place every 3rd summer. It's a two and a half week shindig with parishes from all over the host country taking in pilgrims.
The first half is the Days in the Diocese where pilgrims stay with host families from all over the country and get to know what things are like on a parish level (this was awesome in Germany, I love you Osnabrück and your life-sized foosball game and endless deserts)
The second half is when everyone moves in closer to the epicenter and the major things start happening. There is daily Catechesis (with Bishops and Cardinals), Holy Mass, Eucharistic Adoration, Confession as well as rock and folk Concerts, gymnastics and lots of juggling.
Mostly it's about the anticipation of the one big event where everyone comes together for vespers and mass with the Pope and that is awesome. There's really nothing like camping out with a million other Catholics from all over the world. Maybe it was just because it was my honeymoon, but it was the best experience of my life!
There's a website dedicated to World Youth Day with an about page that explains it as thus:
World Youth Day (WYD) is a worldwide encounter with the Pope which is typically celebrated every three years in a different country. The most recent WYD was celebrated in Madrid from August 16th to 21st, 2011, and the next WYD will be held in Rio de Janeiro, Brazil from July 23rd to 28th, 2012.
WYD is open to all young people who want to take part in a festive encounter with their contemporaries centered on Jesus Christ. This event is an opportunity to experience in first person the universality of the Church; to share with the whole world the hope of many young people who want to commit themselves to Christ and others. World Youth Day is a unique way to deepen your faith and grow closer to Christ, by means of prayer and the sacraments, together with thousands of other young people who share your interests and ambitions.
From that description, it doesn't sound much different in concept than similar Protestant "revival" events that are designed to educate, enlighten, encourage, and enlist youth to grow closer to God, to make commitments, and to encourage a lifetime of service to God and the Faith.
The main difference (other than it being Catholic and not Protestant) is that most Protestant denominations don't have the resources, structure, and organization to make one mega-event. The scope of it is far beyond what most Protestant denominations could dream of.
Other than those factors, it appears that the World Youth Day is remarkably similar to the smaller Protestant events. There is teaching, readings from Scripture (and Catechism), etc. All intended to encourage a closer relationship with God and the Church.