This document summarizes the origins and development of English for Specific Purposes (ESP). It discusses three key trends that contributed to the emergence of ESP: 1) increased demand for English as an international language after WWII, 2) advances in linguistic research, and 3) a focus on learner needs and interests. The document then outlines four phases in the development of ESP, from initial register analysis to skills-based and learning-centered approaches. It emphasizes that ESP is an approach rather than a defined product or methodology.