Encrypting a Mac’s hard drive protects against unauthorised data access should the Mac be lost or stolen. Apple’s FileVault encryption technology basically scrambles data on the hard drive, making the files, photos, messages, videos, and other information useless garbage to others. Unless you have the decryption key or system password, the data is, essentially, irrecoverable.
Mac users can enable FileVault by opening System Preferences, selecting Security & Privacy, choosing the FileVault tab, and clicking the Turn On FileVault button. FileVault may require many hours to completely encrypt the Mac’s hard drive; once encrypted, Macs perform just as they did before the drive was un-encrypted. Users should encrypt laptops and desktops.
When encrypting your Mac you need to take special care to record your passwords. Safely store the recovery key macOS generates somewhere other than on and with the Mac.