Sustainability is a buzzword, a term almost everyone uses, but it seems to be able to signify anything and everything. What does sustainable development really mean? This book provides an introduction to the concept of sustainable development, in all its nuances and interpretations. Starting from the historical process leading up to the Brundtland Report and the Rio Summit, we describe the idea of sustainable development and the main dividing lines in how the concept is understood and used. We also provide an overview of how different actors are working on sustainable development and consider what responsibilities we have to promote sustainable development in our professional capacities.The book is written for anyone who is curious about sustainable development and wants to learn more about what the concept means. We hope that the book will offer you a better understanding of the diverse perspectives included in discussions on sustainable development and give you an opportunity to reflect on your own ideas about what sustainable development requires of us, as individuals and as a society.