Two-factor authentication is akin to protecting your house door with two non-identical locks instead of one. Everytime you want to login, you would need to enter your password, then a code that is sent to your phone, in order to access your account. This way, if someone figures out your password, they still cannot get full access to your account.

Activating 2FA on Facebook Step-by-step: 

1. Open the Facebook app and tap on the menu icon (Three horizontal lines) in the bottom right corner.
2. Scroll down and tap on Settings & Privacy, then tap on Settings.
3. Tap on “Meta Accounts Centre”. 
4. Scroll down and tap on “Password & security”.
5. Under the Two-Factor Authentication section, tap on “Use two-factor authentication”.
6. Follow the prompts to set up 2FA using your phone number or a third-party authenticator app.

Alternatively, you can also enable 2FA on Facebook by visiting the security settings on the Facebook website.

Once you have set up 2FA, you will be prompted to enter a code sent to your phone or generated by your authenticator app when logging in to Facebook from a new device. This helps to keep your account secure by requiring a second form of verification in addition to your password.