Whether or not you know what it is called, you have likely used 2FA at least once in your life online.
Remember the time you tried logging into your email account from a new device and your email service provider sent you an SMS with a PIN (OTP), to re-validate that it was actually you attempting to login? You would have been allowed access to your inbox only after you entered the correct OTP.
Or the time you tried to transfer money to someone through internet banking. Even though you already entered your customer ID and password, your bank’s application would want to make sure that someone else hadn’t stolen your credentials. They do this by sending you an email with a PIN or a link to click on, for additional validation.