Applied linguistics uses knowledge about language, how it is learned, and how it is used to solve real-world problems. It includes areas like second language teaching, literacy, speech pathology, and translation. Applied linguistics has developed over the 20th century through different language teaching methods like the direct method, grammar translation, and audiolingualism. More recently, it views language in holistic and integrative ways rather than discrete skills, and considers the language learner's perspective. It also takes new approaches to teaching the four language skills of listening, speaking, reading and writing. Applied linguistics often lacks definitive answers because language occurs between people and in the mind.