Teaching methods are best articulated by answering the questions, "What is the purpose of education?" and "What are the best ways of achieving these purposes?". For much of prehistory, educational methods were largely informal, and consisted of children imitating or modelling their behaviour on that of their elders, learning through observation and play. In this sense, the children are the students, and the elder is the teacher; a teacher creates the course materials to be taught and then enforces it. Pedagogy is a different way by which a teacher can teach. It is the art or science of being a teacher, generally referring to strategies of instruction or style of instruction. Resources that help teachers teach better are typically a lesson plan, or practical skill involving learning and thinking skills. A curriculum is often set by the Government with precise standards. These standards can change frequently, depending on what the Government states.