If something goes wrong with your Mac accounts, you may still be able to gain access with the Recovery Key.
FileVault hardens macOS by wrapping a layer of login protection around your data. When FileVault is enabled, the data on your startup drive is not immediately available, with just a password between an attacker and your files. That’s a dangerous situation if someone has physical access to your computer—either in your home or office or they’ve stolen it—because there are known and not-yet-discovered methods by which an attacker could try to mount the drive and read files.
FileVault on all Macs puts an additional bar in place: your drive is encrypted and its files unavailable until there’s been a successful macOS login. At that point, the Mac enters into its normal operation mode. (With Intel Macs with a T2 Security Chip and on all M1 Apple silicon Macs, the drive’s contents are always encrypted, but the drive is mounted at startup without an additional step if you haven’t enabled FileVault. Read our explanation from last year about how T2 and M1 Macs interact with FileVault.)
The strong security FileVault offers can also be a problem. Suppose you forget your password (unlikely, I hope!). Or something in macOS breaks or is corrupted in the account login process or files (unlikely, but it happens). In those cases, you may be unable to gain access without knowing your Recovery Key or if you are able to log into iCloud to retrieve a version Apple holds in escrow for you.
Read more at MacWorld.comhttps://www.macworld.com/article/352153/how-to-unlock-your-mac-with-recovery-key-filevault.html