Unlock code from AT&T -- can use any carrier now?

[Guest su6oxone]

I requested an unlock code for my Samsung Blackjack from AT&T (Cingular originally) and I gave them the IMEI code and they said they would send it to me in 5-7 days. Now, I'm unclear if there are several types of unlock codes (app unlock, etc.), but is it correct that this unlock code will allow me to use the Blackjack now with any GSM carrier in the US (or in the world)? I will try to confirm it with a friend's SIM card (is Verizon GSM now? Or just T-mobile?) but I'm curious in the meantime. Thanks for any info!