Cloud computing is a general term for anything that involves delivering hosted services over the Internet. These services are broadly divided into three categories: Infrastructure-as-a-Service (IaaS), Platform-as-a-Service (PaaS) and Software-as-a-Service (SaaS).
Because the managed cloud is built around a high availability private cloud architecture, redundancy is built in with multiple hosts, SAN storage and network security. This provides for failover protection and the unique ability to update and maintain the hardware without a maintenance window.
Amazon Web Services
Amazon Web Services offers a complete set of infrastructure and application services that enable you to run virtually everything in the cloud: from enterprise applications and big data projects to social games and mobile apps.
Windows Azure is an open and flexible cloud platform that enables you to quickly build, deploy and manage applications across a global network of Microsoft-managed data centers. You can build applications using any language, tool or framework. You can also integrate your public cloud applications with your existing IT environment.