FileVault is a feature of macOS that offers full-disk encryption for your Mac. This protects your files if someone were to steal your Mac. Without FileVault, someone with possession of your Mac's hard drive could view the data in your files. With FileVault, that data is encrypted and can't be read. It is unlikely that you will need FileVault, but it is still recommended if you are using a portable MacBook that could easily be stolen. Some companies also have policies that force employees to use disk encryption.
Keeping your Mac free of malware and using strong passwords for your online accounts are two important things you need to do to stay safe and secure. But even if you succeed at these, you can still be vulnerable to common scams that use social engineering to trick you out of your money, privacy and security. Even the most intelligent person can fall victim to a scam if they don’t recognize it when it happens to them. The key to keeping yourself safe is to know the common scams so you recognize them when someone tries to trick you.