Two-factor authentication, also called 2FA or MFA, adds an extra step when logging in.
Instead of using only a password, you also use something else, such as:
An authenticator app code
A push notification
A security key
A one-time code
Why it matters:
If someone steals your password, 2FA can stop them from logging in.
Start with:
Email accounts
Banking accounts
Cloud storage
Social media
Admin accounts