A server is a machine (a computer) that has been configured to respond to requests delivered over the internet. Although one can employ an otherwise unused laptop as a server one more likely rents Capacity on a virtual machine managed by a provider.
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One can run a server on one's own computer that is not much different than using a server in the cloud. One uses the domain name localhost in place of registering a public domain name.
Simulate operating an application in the cloud by running a local file server like those in python 
or deno .
"Serverless" is a misnomer in the sense that servers are still used by cloud service providers to execute code for developers. However, developers of serverless applications are not concerned with capacity planning, configuration, management, maintenance, fault tolerance, or scaling of containers, Virtual machine, or physical servers.