It seems you're looking for a clear, proper explanation of the phrase “romset is unknown FBNeo fixed free” — likely encountered when using FinalBurn Neo (FBNeo) in emulators like RetroArch.
Open FBNeo and go to Help > About. Note the version number (e.g., v1.0.0.3). romset+is+unknown+fbneo+fixed+free
FBNeo is constantly updated. You generally need a "Full Non-Merged" or "Split" romset that matches that specific version's DAT file. Use a ROM Manager (CLRMamePro or RomCenter) It seems you're looking for a clear, proper
When looking for a "fixed" romset, you’ll see these terms. Choosing the right one prevents errors: romset+is+unknown+fbneo+fixed+free