What does it mean to have a loan (Transfer/Sold)

I flunked out of one school back in 2007, I applied for a forbearance and was in a bad place mentally and didn't bother to check up on it. I started going back in 2009 but obviously too late. Now that I'm in a better place mentally, they've started sending me all these overdue bills that I can only assume means the loans are in default because it says Charged off account. I got my credit report and all of them make sense except for one much larger then anything I took out, but it still says its an open account, but its activity designator says Transfer/sold. I really have no idea what this means and could really use some help getting to understand all of this. I swear they make this stuff as confusing as possible.