Refurb's have been retested to ensure they will function before being put up for re-sale. Most of them are bought by people who either discover that the baord will NOT fit into their "Proprietory" case, like a Dell, Gateway, HP, Etc. or they find that they are over their heads in doing the installation, and just decide not to do it.
Usually the motherboard has everything that it's supposed to have as if it was new, but there are times where one of the parts is NOT included then it's sent back - like an IDE Ribbon cable or a USB Bracket.
I've built 3 systems using ABIT re-furbs, and only in one case was there a part missing - a USB Bracket, which I wasn't going to use anyway.
You have to be ready to go with the installation when you get one though, as the time to return it is limited.