Factory carrier-unlocked, works with any cell company that uses the same frequencies, only one I don't think will work is Verizon, or other companies that don't use SIM cards.. AT&T works for sure, T-mobile also works I believe, and many others.
ALSO BOOTLOADER unlocked! This means you can mod it as much as you want, it has a custom recovery and Cyanogen mod pre-installed. Root access has also been unlocked!
Very good condition! No dents or dings, and the screen should be almost mint, it has been covered by a tempered-glass screen protector since about day 3 which ships with the phone.. The protector itself has seen better days, but once removed, the screen should be crystal clear.