The CD-BIOS is the software needed because it is the basic input/output system (or, BIOS) needed to run the Jag CD. Without that software, the emulator cannot recognize what system it is. I don't know, could you consider that a type of firmware? Maybe that is a noob question, but I do not know. But, anyway, all systems have a BIOS. Emulators need that software to mimic those systems. Otherwise, it cannot ascertain what the ROMs can be run under. That explains a bit, anyway. Even PCs and Macs have a BIOS, unless it is called something else on the Mac.