I was coming more from the angle of will new machines get deployed if demand is high, will they shut down if demand is low. I think of cloud machines to have cloud-like features which "just a machine on someone else's network" doesn't have.
Very little thats runs in the cloud is an instance of a physical server. It obviously all ultimately runs on hardware but what anyone using the cloud sees is a virtual instance of a service. There may be one or more virtual instances running for a particular service for a user. Whether additional virtual instances start up and shutdown depending on demand depends on whether you’ve set it up that way and pay for it. On demand scaling like anything is an additional cost and it may be cheaper to pay for a fixed capacity. But what you don’t get is physical hardware booting up and shutting down as that is too slow for on demand scaling. Some services such a AWS lambda are just code from the user point of view and the code runs on demand based on an event trigger such as an incoming https request, and doesn’t run at any other time. Because many services are ultimately just code running on hardware thats already up and running, new instances can start up in a few hundreds of ms, maybe less. Below the surface much is just running on top of Linux on top of the base hardware.
Cloud like features is really just the scale, reliability, storage, memory , and network speed of everything that sits in their data centres across the world. Also the network speeds and latency between them. The Internet has various tiers which describe the speed and priority of the pipes. The pipes the cloud providers are connected to, and their speed can be measured in trillions of bits per second. They will be tier 1, some of the smaller providers that only offer basic website hosting will likely be connected to tier 2.
You could build cloud like services on your own computers if you had the time, energy, and skill. But many cloud services took and take 1000s of man years to design, build, test, deliver then ultimately support.
Here is a screen shot of some of the services available on AWS (Amazon Web Servuces)