The document discusses several factors that affect language learning, including learner characteristics, age, gender, aptitude, motivation, personality, cognitive/learning styles, hemisphere specialization, and learning strategies. It notes that understanding these learner characteristics allows teachers to help students develop positive traits and tailor their teaching approaches to better support different students. Age in particular plays a major role in decisions around how and what to teach, as children, adolescents, and adults learn differently and benefit from different teaching techniques due to variations in maturity levels.