What is cloud computing?

Cloud computing refers to computing resources being accessed which are typically owned and operated by a third-party provider on a consolidated basis in <a href="https://en.wikipedia.org/wiki/Data_Center" target="_blank" rel="nofollow noopener noreferrer">Data Center</a> locations. Consumers of cloud computing services purchase computing capacity on-demand and are not concerned with the underlying technologies used to achieve the increase in server capability.
The applications of cloud/utility computing models are expanding rapidly as connectivity costs fall, and as computing hardware becomes more efficient at operating at scale. The economic incentives to share hardware among multiple users are increasing; the drawbacks in performance and interactive response that used to discourage remote and distributed computing solutions are being greatly reduced.

Grid computing is a term for either of two broad subcategories of <a href="https://en.wikipedia.org/wiki/Distributed_computing" target="_blank" rel="nofollow noopener noreferrer">Distributed Computing</a>:

• Online computation or storage offered as a service supported by a pool of distributed computing resources, also known as <a href="https://en.wikipedia.org/wiki/Utility_computing" target="_blank" rel="nofollow noopener noreferrer">Utility Computing</a>, <a href="https://en.wikipedia.org/wiki/On-demand" target="_blank" rel="nofollow noopener noreferrer">On Demand</a> computing, or <a href="https://en.wikipedia.org/wiki/Cloud_computing" target="_blank" rel="nofollow noopener noreferrer">Cloud Computing</a>. <a href="https://en.wikipedia.org/wiki/Data_grid" target="_blank" rel="nofollow noopener noreferrer">Data Grid</a> provide controlled sharing and management of large amounts of distributed data, often used in combination with computational grids.

• The creation of a "virtual supercomputer" composed of a network of <a href="https://en.wikipedia.org/wiki/Loose_coupling" target="_blank" rel="nofollow noopener noreferrer">Loose Coupling</a> computers, acting in concert to perform very large tasks. This technology has been applied to computationally-intensive scientific, mathematical, and academic problems through <a href="https://en.wikipedia.org/wiki/Volunteer_computing" target="_blank" rel="nofollow noopener noreferrer">Volunteer Computing</a>, and it is used in commercial enterprises for such diverse applications as <a href="https://en.wikipedia.org/wiki/Drug_discovery" target="_blank" rel="nofollow noopener noreferrer">Drug Discovery</a>, <a href="https://en.wikipedia.org/wiki/Economic_forecasting" target="_blank" rel="nofollow noopener noreferrer">Economic Forecasting</a>, <a href="https://en.wikipedia.org/wiki/Seismic_analysis" target="_blank" rel="nofollow noopener noreferrer">Seismic Analysis</a>, and <a href="https://en.wikipedia.org/wiki/Back_office" target="_blank" rel="nofollow noopener noreferrer">Back Office</a> data processing in support of <a href="https://en.wikipedia.org/wiki/E-commerce" target="_blank" rel="nofollow noopener noreferrer">E Commerce</a> and <a href="https://en.wikipedia.org/wiki/Web_service" target="_blank" rel="nofollow noopener noreferrer">Web Service</a>.

A server farm or server cluster is a collection of <a href="https://en.wikipedia.org/wiki/Computer_server" target="_blank" rel="nofollow noopener noreferrer">Computer Server</a> usually maintained by an <a href="https://en.wikipedia.org/wiki/Business" target="_blank" rel="nofollow noopener noreferrer">Business</a> to accomplish server needs far beyond the capability of one machine. Often, server farms will have both a primary and a backup server allocated to a single task, so that in the event of the failure of the primary server, a backup server will take over the primary server's function.
Server farms are typically co-located with the <a href="https://en.wikipedia.org/wiki/Network_switch" target="_blank" rel="nofollow noopener noreferrer">Network Switch</a> and/or <a href="https://en.wikipedia.org/wiki/Router" target="_blank" rel="nofollow noopener noreferrer">Router</a> which enable communication between the different parts of the cluster and the users of the cluster.
Server farms are commonly used for <a href="https://en.wikipedia.org/wiki/Cluster_computing" target="_blank" rel="nofollow noopener noreferrer">Cluster Computing</a>. Many modern <a href="https://en.wikipedia.org/wiki/Supercomputer" target="_blank" rel="nofollow noopener noreferrer">Supercomputer</a> comprise giant server farms of high-speed <a href="https://en.wikipedia.org/wiki/Processors" target="_blank" rel="nofollow noopener noreferrer">Processors</a> connected by either <a href="https://en.wikipedia.org/wiki/Gigabit_Ethernet" target="_blank" rel="nofollow noopener noreferrer">Gigabit Ethernet</a> or custom interconnects such as <a href="https://en.wikipedia.org/wiki/Infiniband" target="_blank" rel="nofollow noopener noreferrer">Infiniband</a> or <a href="https://en.wikipedia.org/wiki/Myrinet" target="_blank" rel="nofollow noopener noreferrer">Myrinet</a>.