I can't seem to find an answer to this probably because it's such a simple thing that it doesn't occur to anyone that it might need to be explained. But I'm not clear on something very simple.

 

So basically, I build a PC however I want, like I was going to use it as a desktop, and then install Unraid on it?

 

And I can use internal SATA HDDs vs USB HDDs?

Unraid is the operating system. You can host other operating systems as VMs on Unraid. Unraid storage needs to use SATA connections 

Great! Thank you. I thought that's how it would be, but I wasn't sure.