A server can just be a PC left working in a corner, depnding on what specifically you’re doing with it. Hardware designed to be a server tends to have more power in the places that matter for that job and less (if any) power dedicated to home use stuff like graphics.

I have a server for my family (WELL mostly me and my father). It consists of an old gaming PC with Linux Server Stuff installed on it. Doesn’t need to be anything more, it’s just Emby (media, mostly films) and NAS stuff.

It’s mostly intent and what you run on it.

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.

I’d define a server as a computer that is primarily interacted with through other networked devices.

Hardware/software doesn’t have much to do with it; you can have a server do basically everything you’d need running on windows 11 if you’re a masochist.

A PC can be a server. A server can be a PC.

Famously Google use commodity PC hardware to build the v1 version of its search engine: