Password-protecting your website has many benefits. It's most commonly used as a feature for protecting "free" courses & videos which is shared internally within a company or group.
To password-protect your website;
Go to your website/landing page editor
Click on "Dashboard" on the left side panel
Click "Pages"
Hover over your page(s) of choice, and click the lock icon. Then, set your password of choice, and voilà - it's now password protected.