A catechism is a book or a set of questions and answers that helps teach people about religion, especially Christianity. It explains the basic beliefs and principles of the faith in a simple and organized way. Full definition
In Catechism of the Catholic Church 2181 the Pope has written «The Sunday Eucharist is the foundation and confirmation of all Christian practice. (faith.org.uk)
As to how it started, the new Catechism says that the account of the Fall in Genesis uses figurative language, but it does affirm a primeval event (309). (faith.org.uk)
When one adds to the Bible such forms as catechisms, theological propositions, literary sources not based on the Bible, and the normal discourse of teaching situations, it is clear that the results are less than satisfactory. (religion-online.org)