"Cloud computing, often referred to as simply “the cloud,” is the delivery of on-demand computing resources—everything from applications to data centers—over the Internet on a pay-for-use basis. The cloud is essentially a set of distributed systems that are servers, applications, and databases to new a few, that are hosted by a major provider such as Amazon, Microsoft or Google. Their responsibility is to offer you the infrastructure needed to host your applications so that you don’t have to worry about managing a data center, but instead focus on building a great application for your customers. The benefits of cloud computing include reduced costs, and faster delivery of content/applications. Since the advent of cloud computing many companies now operate entirely in the cloud, such as Netflix and Facebook."
in other words
Getting your vegetables from a grocery store rather than growing them yourself.