The 15th ordinary Synod of Bishops is meeting now to discuss young people, the faith, and vocational discernment. Many have referred to this nearly month-long meeting as the "Youth Synod." This raises a question: What is a youth?

In the eyes of the Vatican, a youth is defined as a person between the ages of 16 and 35.

This age range extends beyond what is typically considered a "youth" in the United States. Whereas American World Youth Day participants are frequently groups of Catholic high school students accompanied by chaperones, many have observed that World Youth Day participants from European countries tend to be in their 20s and 30s.

With that established, what is a synod? A synod is a meeting of bishops gathered to discuss a topic of theological or pastoral significance, in order to prepare a document of advice or counsel to the pope.

The Synod of Bishops was created in 1965 by Pope Saint Paul VI, who was canonized earlier this week. Paul VI charted the synod to encourage close union between the pope and the world's bishops and to "insure that direct and real information is provided on questions and situations touching upon the internal action of the Church and its necessary activity in the world of today."

Ordinary synods happen every three years on issues voted upon by synod delegates elected or appointed from each continent, and from certain Vatican offices. There have been 15 ordinary synods to date. There are also extraordinary synods and special synods.

What makes a synod extraordinary? It is a matter of timing. Extraordinary synods are called by the pope outside of the usual timing as a matter of urgency.

Special synods address a particular topic and are usually regional. For example, next year there will be a Special Synod on the Pan-Amazonian Region.

Instrumentum Laboris is Latin for "working document." It is developed before the meeting by a small working committee of Vatican officials and diocesan bishops, and frames synod discussions. During a synod, bishops make comments and observations on the working document, and meet in small discussion groups to propose changes to the text, or to suggest new texts and additional areas for consideration.

A Post-Synodal Apostolic Exhortation is a document produced by the pope after synod assembly concludes. It generally reflects the recommendations made by the synod in its final document submitted to the pope, along with his own reflections.

The most recent post-synodal apostolic exhortation was Amoris laetitia, which was released after the 2015 synod on the family.

New rules for the 2018 synod of bishops say that the pope may approve, as a part of the Church's magisterium, the final report from the synod fathers instead of producing a separate exhortation. It is not yet determined whether Pope Francis will do this at the conclusion of the synod.

Synod Fathers are the bishops and others who participate and vote in a synod.

Auditors are people appointed by the pope to participate in synod discussions and interventions within the synod hall, but without a vote on documents. Laypeople and women religious participate in the synod as auditors.

In a historic first, the 2018 Synod of Bishops has invited 34 young people participating as auditors.

Circoli Minori are small discussion groups in which synod participants who speak a common language work together to produce a report on each section of the working document, along with modi, or proposals, to be included in the final document.

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At the 2018 Synod of Bishops, there are 14 language groups -- four in English, three French groups, three Italian, two Spanish, one German group, and one Portuguese.

"Synodality" is generally understood to represent a process of discernment, with the aid of the Holy Spirit, involving bishops, priests, religious, and lay Catholics, each according to the gifts and charisms of their vocation. This phrase has been emphasized in Pope Francis' pontificate. In May, the International Theological Commission released a document on "Synodality in Life and Mission of the Church."