This introduction presents an overview of the key concepts discussed in the book, which focuses on the wealth of research undertaken by sociolinguists concerned with language variation and use in society. The core of this specialisation comes from those working in the field of language variation and change. Chomskyans sought to define the essence of language in mentalistic grammars of so abstract and broad a nature that they could capture the entire human capacity for language. It is thanks to the Chomskyan revolution that we have learned an impressive amount about how humans acquire language, store it in the mind, and process it. Linguistics is a fascinating subject in both its sociolinguistic and non-sociolinguistic (cognitive-biological) aspects. This linguistics would embrace the dialectics of langue and parole and competence and performance. The book provides a practitioner's overview of the multifaceted field of sociolinguistics that is an integral part of that linguistics.