Cloud computing is the on-demand delivery of compute power, database storage, applications, and other IT resources through a cloud services platform via the internet with pay-as-you-go pricing. In other words, if you intend to start any project or business you need IT resources and if you procure these IT resources at your own it might be very costly and involve fixed as well as variable cost. Cloud computing is making these IT resources available to you on pay as you consume basis, thus reducing your fixed and variable costs to a large extent. Amazon is one provider of such services like cloud computing.
Cloud computing provides a simple way to access servers, storage, databases and a broad set of application services over the Internet. A Cloud services platform such as Amazon Web Services owns and maintains the network-connected hardware required for these application services, while the user provision and use what he needs via a web application.
Cloud computing has three main types that are commonly referred to as Infrastructure as a Service (IaaS), Platform as a Service (PaaS), and Software as a Service (SaaS).