When companies, governments or academics needed extra computing power or space they used to go out and buy more machines. Nowadays they can get these services more flexibly, by using the cloud.
So what exactly is the cloud?
Clouds allow access to remote computing services, which are generally delivered by a single party. Users only have to pay for what they use, when they want to use it.
Clouds differ from grids in that they are less about collaboration and sharing and more about providing access to extra computing services as and when it is needed. For those wanting to quickly increase or decrease computing capacity the cloud can provide a solution.