Cloud computing is a style of computing in which dynamically scalable and
often virtualized resources are provided as a service over the Internet. Users
need not have knowledge of, expertise in, or control over the technology
infrastructure in the "cloud" that supports them.
The concept incorporates infrastructure as a service (IaaS), platform as a
service (PaaS) and software as a service (SaaS) as well as other recent (ca.
2007-2009) technology trends that have the common theme of reliance on the
Internet for satisfying the computing needs of the users. Cloud computing
services usually provide common business applications online that are accessed
from a web browser, while the software and data are stored on the servers.
The term cloud is used as a metaphor for the Internet, based on how the Internet
is depicted in computer network diagrams, and is an abstraction for the complex
infrastructure it conceals.