Those are both terms that apply to federal student loans.
It refers either to a creditor seeking payment from the government on a federally insured student loan, or that the government (Dept of Education) hass obtained rights to pursue collection of the delinquent loan.
I assume that you currently have a delinquent federal student loan that is either with a credtor but insured by the U.S. government, or that you have a federal student loan that has been referred to Dept of Ed for payment of the remaining balance.
What are the details of the current status of your federal student loan?
Definitely check out the NSLDS website to see who currently has the loan - it could be a servicer or guarantor.
Was this an FFEL loan? "Back in the day" private banks issued student loans that were guaranteed by the feds, so even though it sounds like it was a private bank, it could still be a federal loan. I would probably also contact the loan servicer/guarantor to see what the status of the loan is. As Sabii noted, it sounds like you may be able to get it discharged through disability.