The only definite distinction is that one provides the service, and the other uses the service.

There is absolutely zero requirement for the hardware or software to be different, aside from changing the configuration to perform the desired task.

You can have two exactly identical machines, one can be a DHCP server, and the other a client. The only difference is that one is configured to act as a DCHP server. This doesn’t need different software necessarily, just different settings.

Please Ukraine, don’t give that clown what he wants. He’ll just keep extorting other countries.

There are these things called books…

Not yet, not necessarily. The further this goes, the closer they come to the point of no return.