The network. Clouds generally refer to wide area networks (WANs) such as the Internet, but can also refer to a private cloud, which is a company's own network. However, the term "cloud computing" most always refers to the public Internet and not to private networks (see cloud computing).
A cloud-like symbol in a network diagram is used to reduce an entire communications network into points of entry and exit. An actual cloud symbol is drawn when the network architecture is not material to the illustration. Inside the cloud, there may be any number of cables, servers, routers, switches and other network devices.
The cloud symbol represents a communications network without specific details of its architecture. Diagrams use cloud symbols when only the points of entry and exit need to be identified.