"Blessed are the poor in spirit: for theirs is the kingdom of heaven."
What is Catechesis?
"The word katechesis means instruction by word of mouth, especially by questioning and answering. Though it may apply to any subject-matter, it is commonly used for instruction in the elements of religion, especially preparation for initiation into Christianity. The word and others of the same origin occur in St. Luke's Gospel: "That thou mayest know the verity of those things in which thou hast been instructed" (katechethes, in quibus eruditus es — i, 4). In Acts 18:25, Apollo is described as "instructed [katechemenos, edoctus] in the way of the Lord". St. Paul uses the word twice: "I had rather speak five words with my understanding, that I may instruct [katecheso, instruam] others also" (1 Corinthians 14:19); and "Let him that is instructed [ho katechoumenos, is qui catechizatur] in the word, communicate to him that instructeth [to katechounti, ei qui catechizat] him, in all good things" (Galatians 6:6). Hence the word, with its technical meaning of oral religious instruction, passed into ecclesiastical use, and is applied both to the act of instructing and the subject-matter of the instruction."
(Thomas Scannell, "Christian Doctrine," The Catholic Encyclopedia. Vol. 5.)