A "RetroArch BIOS pack" is a collection of necessary firmware files required by various emulation cores (like PlayStation, Dreamcast, or Saturn) to function correctly. While RetroArch includes most basic cores, it does not provide these proprietary BIOS files due to legal restrictions.
Not every system needs a BIOS, but the following are the most common ones that do: Retro Game BIOS Files - What are they? Where? Which ones? retroarch bios pack
BIOS files are copyrighted code. Sony owns the code inside the PlayStation BIOS. Nintendo owns the code inside the GameBoy Advance BIOS. A "RetroArch BIOS pack" is a collection of