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 WhatsApp Step-by-step using Android: 

1. Open WhatsApp and tap on the three-dot icon at the top right corner of the screen. From the drop-down menu, select "Settings."
2. Navigate to Account Settings In the "Settings" menu, select "Account" to access your account settings.
3. Access Two-Step Verification Settings Scroll down and select "Two-step verification" to access the two-factor authentication settings.
4. Enable Two-Step Verification Tap the "Enable" button to turn on two-step verification. You will be prompted to enter a six-digit PIN code that will be required whenever you try to verify your phone number on WhatsApp.
5. Confirm the PIN: Re-enter the six-digit PIN to confirm it.
6. Add an email address: You can optionally add an email address to your account for additional security. If you forget your PIN, you can reset it using the email address associated with your WhatsApp account.
7. Save changes once you have entered your PIN and email address (if applicable), tap on "Save" to enable two-step verification.

Activating 2FA on WhatsApp using IOS Step-by-step: 

1. Open WhatsApp and go to the Settings.
2. Tap on "Account."
3. Select "Two-step verification."
4. Enable the option.
5. Enter a six-digit PIN of your choice.
6. Confirm the PIN.
7. Add an email address for account recovery (optional but recommended).
8. Save changes.

That's it! Two-factor authentication is now enabled on your WhatsApp account. From now on, whenever you try to verify your phone number on WhatsApp, you will be required to enter the six-digit PIN you created. This adds an extra layer of security to your account and helps prevent unauthorized access.