This is confusing:

Host: "Turn on hosting only for the Host computer or where the company file is stored."

Server: "computer that physically stores your company file"

How is the host different from the server? Sounds like they're the same computer, but you also say, "If you're using a server to host your file, one computer still has to act as a Host. You must not turn on hosting for workstations."

So, which is required? The server or the host or both? And which computer has the data and do both/all computers have to have QB installed?