Two-Factor authentication (2FA) is available on most major services; think Gmail, Facebook, Twitter, etc. But what is it?
Simply put, 2FA enhances the security of your account by requiring an additional factor when logging-in. So instead of simply logging-in to a service with just a username and password, a multi-digit code will be required as well, thus reducing the ability of hackers to access your account with a compromised password.
It is easier to manage than it sounds and it is well worth the effort. PC Magazine has written an excellent article further describing this process including how-to guides for a number of popular service providers.
Here is a list of services currently offering some form of 2FA.