The two firmware types are Initiator Target (IT) and Integrated RAID (IR). IR is the typical hardware RAID firmware that the internal cards or boards ship with.
The IT firmware, on the other hand, is the Initiator Target firmware which is designed to allow a SAS HBA to connect to up to 256 devices using SAS Expanders. The IT firmware is typically shipped on external cards. The IT firmware does not have any RAID capabilities and simply acts as an HBA.