Though many research studies have been conducted in the field of implicit and explicit knowledge by world renowned researchers like Stephen Krashen, Ellen Bialystok, Robert DeKeyser, Rod Ellis, Nick Ellis, Catherine Elder, Shawn Loewen, Rosemary Erlam and Jenefer Philp etc, the novelty of my research work lies in the fact that it is the first research study which has been carried out in the field of implicit and explicit knowledge in relation to the medium of instruction for the teaching of English as a second language in an EFL context i.e. Pakistan. In my view, the contents of this book are important in two ways. On the one hand, they provide the reader with an introduction of the basic concepts, terminology and previous research carried out in the field of implicit and explicit knowledge. On the other hand, it opens a new horizon of research in the field of implicit and explicit knowledge in relation to language learning context and medium of instruction. I hope that this book will serve its intended purpose and will prove to be a good source for facilitating further research.