The document discusses the evolution of ESP (English for Specific Purposes) as an approach to language teaching. It notes there have been shifts in ESP theory and practice over time, with different stages focusing on linguistic aspects, but all taking an essentially language-centered approach. ESP is defined as not a product or variety of English, but an approach where all decisions around content and method are based on meeting the specific needs of learners. The document outlines various branches of ESP including English for academic, occupational, and vocational purposes.