The newsreels report on it every day, every politician in the campaign promises to eradicate it, the ordinary citizens suffer it -or use it to save the penalty of complying with the law-, many public officials consider it a consubstantial element in their charge : Corruption is a serious and widespread social disease. In this very brief introduction, Leslie Holmes contrasts the various definitions used to define a phenomenon that erodes public confidence, hinders the functioning of the economy, undermines the environment, undermines the security of people, allowing the proliferation of organized crime. And adventure psychosocial and cultural explanations to understand the rise of corruption in its many forms: bribes, exchange of favors, white collar crime, deterioration of institutions. The reader will find here conceptual tools to understand this harmful practice, to measure it and to confront it from different fronts, the same from the State as from organized civil society.