This chapter analyses, what different organisations and entities refer to as 'corruption', its causes, as well as the varying understandings of the effects of the phenomenon on societies under distinct circumstances. This will be useful in assessing whether international organisations' as well as countries' international development departments' anti-corruption efforts are focused where they are likely to have the highest potential to translate into meaningful and long-term improvements in societies. As Transparency International (TI) and other institutions working in the sphere have recognised, it is not viable to restrict the understanding and focus of anti-corruption activities to those involving the public sector. The chapter discusses the conceptual approaches to corruption, including the definitions used by the international agencies that attempt to combat it globally, noting the inadequacy of the definitions for the complexity of the phenomenon in question, such as the sometimes blurry distinction between activities that are mostly frowned upon and those that are illegal.