Cloud computing means Internet ('Cloud') based development and use of computer technology ('Computing'). It is a style of computing where IT-related capabilities are provided “as a service”, allowing users to access technology-enabled services "in the cloud"without knowledge of, expertise with, or control over the technology infrastructure that supports them. It is a general concept that incorporates software as a service, Web 2.0 and other recent, well-known technology trends, where the common theme is reliance on the Internet for satisfying the computing needs of the users.
The majority of cloud computing infrastructure currently consists of reliable services delivered through next-generation data centers that are built on compute and storage virtualization technologies. The services are accessible anywhere in the world, with The Cloud appearing as a single point of access for all the computing needs of consumers.
The cloud computing "revolution" is being driven by companies like Amazon, Google, Salesforce and Yahoo! as well as traditional vendors including Hewlett Packard, IBM, Intel and Microsoft and adopted by individuals through large enterprises including General Electric, D&B, L'Oréal, Procter & Gamble and Valeo.
Capital expenditure minimized and thus low barrier to entry as infrastructure is owned by the provider and does not need to be purchased for one-time or infrequent intensive computing tasks. Services are typically being available to or specifically targeting retail consumers and small businesses.
Multitenancy enabling sharing of resources (and costs) among a large pool of users, allowing for:
Centralization of infrastructure in areas with lower costs (eg real estate, electricity) Peak-load capacity increases (users need not engineer for highest possible load levels)
Utilization and efficiency improvements
Scalability which meets changing user demands quickly. Massive scalability and large user bases are common but not an absolute requirement.
Reliability by way of multiple redundant sites, which makes it suitable for disaster recovery
Security which typically improves due to centralization of data, increased security-focused resources, etc. but which raises concerns about loss of control over certain sensitive data
Performance is monitored and consistent but can be affected by insufficient bandwidth or high network load.
Device and location independence which enables users to access systems regardless of location or what device they are using (eg PC, mobile).