Cloud computing encompasses a number of different services. One set of services, sometimes called software as a service (SaaS), involves the supply of a discrete application to outside users.
The application can be geared either to business users (such as an accounting application) or to consumers (such as an application for storing and sharing personal data).
A second set of services, variously called utility computing, grid computing, and processing as a service (PaaS), involves the provision of computer processing and data storage to outside users, who are able to run their own applications and store their own data on the remote system.
A third set of services, sometimes called platform as a service (PaaS), involves the supply of remote computing capacity along with a set of software-development tools for use by outside software programmers.