File and Folder Permissions

Hello All,

I am going to sound like a newb even though I am not...I think. I am trying to understand permissions on files and folders. When I first started looking at it on my Windows 7 Ultimate computer I noticed that some of the permissions were for Administrators and Sean and Users, Service you get the idea. It seemed pretty easy to me.

I lost interest and moved on to other things (I even named my computer TWOOFSIX hint....that comes into play later) and then I found myself back there again recently and I have had to add myself and other groups to some folders and files. But I am confused because now when I add a group or person it ALWAYS gets added as TWOOFSIX\Administrator or TWOOFSIX\Sean.

Here is my confusion as far as I know having the TWOOFSIX\ means I am part of domain. Is that incorrect? I can tell you I am not part of a domain, my computer is not part of a domain except for Workgroup which I can't leave!!

So why before was it just Administrator, Sean, Service, etc...and now it's TWOOFSIX\......does that mean domain? Or something else? Any information is greatly appreciated and yes I have checked the microsoft site and it was out of my depth. Thank you all very much!