Sustainability is the capacity to support, maintain, or endure; it can indicate both a goal and a process. Sustainability can be maintained at a certain rate or level, as in sustainable economic growth. In ecological studies sustainability describes how biological systems remain diverse, robust, and productive over time, a necessary precondition for the well-being of humans and other species. Social sustainability is often conceived in terms of sustaining the well-being of people. Environmental sustainability refers to sustaining nature or natural resources. Sustainability has been re-defined as the integration of the environmental, economic, and social dimensions. The Global Reporting Initiative provides all companies and organizations with a global sustainability-reporting framework. Social sustainability is often conceived as well-being and includes physical, social, and emotional needs as well as health or the subjective perception of happiness. The chapter also presents an overview of the key concepts discussed in this book.