ESP emerged after World War 2 due to increased international scientific and economic activity, the dominance of English in technology and commerce, and a focus on learning English for professional purposes rather than pleasure. It developed from a focus on describing English grammar and rules to analyzing how English is used in real communication contexts. ESP is defined as an approach rather than a product, tailored to meet learners' specific needs and using language appropriate for their target disciplines and activities. Key aspects include being needs-based, focusing on language used in particular contexts, and emphasizing effective learning over prescribed methods.