What is two-factor authentication and do I need it?
Answer first
Signing in requires a second check alongside the password, such as a code from an app. Turn it on at least for email and important accounts.
A password can be exposed through a service breach or a phishing page even when you otherwise act carefully.
The second factor makes it harder to use a stolen password on its own. Store the service’s recovery codes somewhere safe too.
Email deserves priority because many other services send their password-reset links there.
Turning it on is usually free. Start with email, then continue with accounts holding payment or personal data.