Cloud Computing. It is a computing capability that provides convenient and on-demand network access to a shared pool of configurable computing resources. These resources can be rapidly provisioned and released with minimal management effort or vendor interaction. Cloud computing has six essential characteristics: pay-per-use, self-service,broad network access, resource pooling, rapid elasticity, and measured service. In general terms, cloud computing enables three possible modes: Infrastructure as a Service (IaaS), Platform as a Service (PaaS),and Software as a Service (SaaS). It can be public, private, or hybrid.