The term “cloud” is so ubiquitous that it means different things to everyone. For these purposes, we will define it in relation to infrastructure; the cloud is the ability to auto-provision a subset of available compute/network/storage to meet a specific business need via virtualization (IaaS).
As far as applications, the cloud is browser-based access to an application (SaaS), and, importantly, the utility-based consumption model of paying for these services that has caused a major disruption in the traditional models of technology.