Catechismus ad parochos ex decreto Concilii Tridentini editus et Pii V

This is the Roman Catechism, also known as the Catechism of the Council of Trent, which was written for use by parish priests in their instruction of the lay faithful. It was published in 1566, but has gone through numerous editions since that time. It covers the four main parts of Christian Doctrine: the articles of belief in the Apostle's Creed; the means of grace in the Sacraments; the rules for moral conduct in the Decalogue (i.e. 10 Commandments); and the manner of prayer in the Lord's Prayer (i.e. the Our Father).
It is available in english translation from TAN books and publishers, inc.