A catechism is a summary or exposition of doctrine and serves as a learning introduction to the Sacraments traditionally used in catechesis, or Christian religious teaching of children and adult converts. As Daniel R. Hyde has shown, this word is used in the New Testament for the instruction of believers. Catechisms are doctrinal manuals—often in the form of set questions and answers to be memorized—a format that has been used in non-religious or secular contexts as well.