Blacklisted devices are ones that have been reported stolen or lost, and the owner has blocked the IMEI number. The IMEI number is unique to a device — there is only one per device. Blacklisted phones are not accepted by BuyBack.
A device is greylisted if it has been blocked by a carrier due to unpaid bills. Greylisted phones are not accepted by BuyBack.
Unlocked devices are ones that are not tied to a specific carrier. Unlocked devices are accepted by BuyBack. More info on locked vs. unlocked devices
A jailbroken or rooted device is one that has been modified to bypass a manufacturer’s security restrictions, which enables the download of applications or extensions not offered by the official Apple or Google Play stores. This practice is illegal, and jailbroken or rooted devices are not accepted by BuyBack.
A device is counterfeit if it is a fraudulent reproduction of an existing brand. Counterfeit devices are illegal and not accepted by BuyBack.
A foreign device is one that was manufactured specifically for use outside of the United States. This means that the device may not work, or may work with some idiosyncrasies, when used in the US.
For example, some iPhones are built specifically for Japan, and because of Japanese laws they are set up to have the camera sound on all the time. Other foreign phones simply don’t work with the cellular data networks offered in the US because they are built for other countries’ frequencies. Foreign devices are not accepted by BuyBack.