Basically, it’s to do with securing your logins, so that there’s more than one link in the chain needing to be broken before an unwanted intruder can get in your website.
By default, your WordPress accounts are protected by only one thing: your password. If that’s broken, then everything’s wide open.
“Two factor” means adding a second requirement. Usually, this is a code that comes to a device you own (e.g. phone, tablet) – so, someone can’t get into your website without getting hold of your device. You can get a longer answer from Wikipedia.
Sometimes it is also called multi-factor authentication instead of two-factor – because someone could secure their systems with as many factors as they like.
Posted in: Two Factor Authentication