What is two-factor authentication (2FA) and why do you need it?
The short answer
Two-factor authentication adds a second lock to your account. Besides your password, a code from your phone or a confirmation in an app. Even if your password leaks, an attacker still cannot get in. Enable it at minimum on your email, bank, and password manager.
In detail
Passwords leak through data breaches, phishing, or shoulder surfing. Two-factor authentication catches that by demanding something an attacker does not have. A code that changes every thirty seconds, a prompt on your phone, or a physical key. The effort for you is seconds. The barrier for an attacker becomes nearly insurmountable.
Not all 2FA is equal. Codes via SMS are better than nothing but interceptable. App-based codes (TOTP) are better, and passkeys or hardware security keys are the strongest. Many password managers can generate those app codes themselves and fill them right after the password. Bitwarden Premium, Proton Pass Plus, and 1Password have it built in, keeping everything conveniently in one vault.
Start with the accounts that unlock everything else. Your email (it resets every other password), your bank, and the password manager itself. And when you set it up, always save the recovery codes. They are your lifeline if your phone goes missing.