This document discusses concepts, nature, and purposes of curriculum development. It defines curriculum broadly as the total learning experiences of individuals, including both in-school and out-of-school experiences. The document outlines different models of curriculum development, including traditional models focused on subjects/disciplines, and progressive models emphasizing experiences. It discusses key thinkers and reforms in curriculum in the Philippines. Ralph Tyler's influential 4-step model and Hilda Taba's linear model of curriculum development are also summarized.