The listed servers below are currently offline to perform a BIOS Update. This can take up to 30 minutes and more if any not expected issues occur. Update: Maintenance is completed and all servers are back up. Spoiler: Completed Age of Engineering Node 1 BevosTechPack Ferret Business Galactic Science Infinity Skyblock Tekkit Legends (old node) Beyond Crackpack Direwolf20 1.10 ForeverStranded Skyfactory3 Node 2 Agrarian Skies 2 Project Ozone 2 Kappa Regrowth Skyfactory 2 Age of Engineering Node 2 Age of Engineering Node 3 Infinity Evolved Expert Node 5 Infinity Evolved Normal Node 5 Skyfactory 3 Node 1 Tekkit Legends (new node) Crundeecraft Direwolf20 Node 1 Infinity Evolved Expert Node 4 Infinity Evolved Normal Node 4 Infinity Evolved Expert Node 1 Infinity Evolved Normal Node 1 Direwolf20 Node 2 Infinity Evolved Node 6 Project Ozone 2 Agrarian Skies Agrarian Skies + B-Team CrashLanding
Basic Input Output System, it provides low-level system settings and connection between your OS and hardware.
Unless you pull your power supply in the middle of the update, you should be safe. And even in those cases modern PCs might have some kind of a fallback solution, actually not sure about that. And directly deleting a BIOS is not that easy as it sounds, at least not by accident.