On my tax form provided by my broker, all transactions from 2016 are grouped into 4 categories, which are all combinations of "short term/long term" and "basis reported to the IRS/nor reported to the IRS". I understand what "short term/long term" means but I'm not sure what the second qualifier means.
Read about cost basis reporting from the IRS. Starting in 2011, the main responsibility for tracking cost basis shifted from the taxpayer to the brokerage. Your brokerage is saying you purchased this asset before the change took place, or it was transferred to you, so they're not required to report a basis to the IRS. You should have this information in your records, and you'll need to use it to properly determine the correct capital gain or loss.