What these companies do is provide the data and computing infrastructure to build applications on top of. This means that they do not build your network for you but host it, every customer is different thus may have specific requirements pertinent to them only. So in essence you can build, manage and host your entire network on a cloud hosting provider if that is what you require. However the cloud provider only provides the hosting and data management functionality, while the customer builds whatever front end application or network that they require. Many computer solutions, application or network can be hosted and serviced from the cloud and any of the mentioned cloud service providers can supply the necessary infrastructure to bring most projects to fruition. Any server functionality that is available at a physical location is also available from a cloud service.