Originally viewed as a macro-level endeavor, where governmental planners decided on how language is used, taught, learned and developed in social life, language policy and planning has emerged as both an interdisciplinary and specialized field in the mid-twentieth century. This introduction presents an overview of the key concepts discussed in the subsequent chapters of this book. The book analyzes the negotiation of linguistic identity in two minority settings in Italy and Croatia not recognized as national minorities in their respective nations. It explores agency in the language planning initiatives and motivations of heritage language maintenance in the South Sudanese diaspora of Australia. The book also explores a second language teacher education program at the University of San Diego in which teacher candidates participate in practicum experiences within a community based English language program. It explores agency as part of policy aimed at increasing linguistic diversity in Australian secondary schools.