How old is the Catechism of the Catholic Church, and in what manner was it conceived and instituted?
The current Catechism of the Catholic Church is what is known as a universal catechism; that is, a catechism intended to apply for, and meant for the usage of, the entire Catholic Church. The only prior published universal catechism is the Roman Catechism or Catechism of the Council of Trent, which was published in 1566 at the direction of the Council of that name.
Today's Catechism largely follows the organization of the Roman Catechism: it goes through each clause of the Apostles' Creed, then discusses each of the Sacraments in turn (together with certain other liturgical celebrations), then (after a discussion of sin and morality) runs through the Ten Commandments, and finally turns to a discussion of prayer, beginning with prayer in general, and wrapping up with the Our Father/Lord's Prayer.
The edition of the Catechism available on the website of the U.S. Conference of Catholic Bishops contains the text of the apostolic constitution Fidei Depositum, which accompanied the first publication of the Catechism (in French). This document describes the history of the publication.
In January 1985, Pope St. John Paul II convoked an extraordinary synod of the council of bishops, to celebrate the 20th anniversary of the 2nd Vatican Council. The synod expressed a general desire for a new catechism for the universal Church, and so the following year the Pope organized a commission to draft one.
According to Fidei Depositum, the project went through several revisions, including consultation with individual bishops, with councils of bishops, and with theologians and schools of theology. The French-language version was for some reason the first to be published; in 1993, shortly after its publication, work began on the definitive edition in Latin (the "editio typica"). This was published in 1997, accompanied by the apostolic letter Laetamur Magnopere. All subsequent publications are derived from this edition.
Although the Catechism is new, its contents are not. Nearly every book in the Catholic Bible is quoted at least once; so are most of the Church's ecumenical councils starting with the first council of Nicaea. In addition, many particular councils are cited, and the writings (mostly encyclicals) of 22 popes. The Roman Catechism is often used as a source, as are the Church's liturgical documents (pre-eminently the Roman Missal and Liturgy of the Hours) and the writings of many, many theologians and saints, from Ignatius of Antioch (1st-2nd century) to Blessed John Henry Newman (died 1890). The full list of citations is available here (part 1), here (part 2), and here (part 3).