What’s the value-add over just buying a SFF PC?

This happened to me years ago (the .com of my full name). I kept checking in at expiry date for 3 years and they eventually let it expire, so I bought it back for normal price.

So it’s a computer that lets you remotely control another computer? Is the advantage over SSH or remote desktop etc that you can interact with stuff outside the OS, like in BIOS?

I’ve never heard of this particular “Longhorn” and was very confused as to why Windows Vista was coming up in conversation.