The Heidelberg Catechism (1563), one of the Three Forms of Unity, is a Reformed catechism taking the form of a series of questions and answers, for use in teaching Reformed Christian doctrine. It was published in 1563 in Heidelberg, Germany.[1]: 230 Its original title translates to Catechism, or Christian Instruction, according to the Usages of the Churches and Schools of the Electoral Palatinate. Commissioned by the prince-elector of the Electoral Palatinate, it is sometimes referred to as the 'Palatinate Catechism.' It has been translated into many languages and is regarded as one of the most influential of the Reformed catechisms. Today, the Catechism is 'probably the most frequently read Reformed confessional text worldwide.'[2]: 13