The document defines and describes several key concepts in language teaching and learning: - The zone of proximal development refers to what a learner can do with help versus without help. - Total physical response uses actions and physical movement to teach language to young children through following teacher instructions. - The target language is the language being studied, while one's mother tongue or native language is their first language. - Approaches are methods used by teachers to instruct language, while acquisition involves natural communication versus learning with a focus on language forms.