Cloud computing is changing the way computing is undertaken. It provides the ability to access IT resources on demand without the need for significant capital expenditure, thereby lowering the entry barriers for new entrants in multiple sectors. Cloud computing has thus become a platform for innovation. This report presents the concept of cloud computing, the services it provides and deployment models, and thus give a clear overview of what it is and what it is not. It provides an overview of how cloud computing changes the way computing is carried out, and evaluates the impacts of cloud computing (including its benefits and challenges as well as its economic and environmental impacts). Finally, the report discusses the policy issues raised by cloud computing and the role of governments and other stakeholders in addressing these issues.