In simple terms, the is the firmware that boots the console. For the Neo Geo, it controls:
Description. neogeo.zip. A zip file containing one or more Neo Geo BIOS files. SNK - Neo Geo | Onion Download Neo Geo Bios Rom -Neogeo.Zip-
This is the most critical section. The Neo Geo BIOS is owned by SNK Corporation (now SNK Playmore). In simple terms, the is the firmware that boots the console