2 Factor Authentication or Two Factor Authentication (TFA) is a way to better secure your online accounts. In addition to the password with your account, you enter an additional code with TFA that you generate via one for your personal device.
TFA is an authentication process where two of the three factors are needed to recognize you as a valid user
Something that knows - This is your password, PIN code, access phrase or a similar code.
Something you have - You can think of a smart card, a card or other hardware.
Something you "are" - This is, for example, your fingerprint, pattern of your iris, voice recognition or your heartbeat.
TFA works if two of the three have been used correctly.
An example of everyday life: If you are going to pin, you need two things: a card and your PIN code. Your bank card is something you have, you know your PIN code. With this combination, you get access to your bank account. If someone has your pass but does not know your pin code, it stops. The other way around is identical, there is a list online with all PINs, but without a bank card, you will not get far.
How does this authentication work?
The good news is that you can set up TFA fairly quickly and that it works in almost the same way with every service. The bad news is that you always have to set it up yourself and you sometimes have to find where you do the configuration.
TFA works on almost every site according to the same principle: After giving your login name and password you have to enter an extra code or text that you receive via an extra app as Authenticator or via SMS. Only after entering this extra code you will gain access to the secured part of the site. If a website offers TFA, you will often have to activate it yourself. We will show you how to set up TFA for Google Gmail. The method is virtually identical for any other service that TFA offers, but sometimes names and terms will differ slightly.
Where do you use it?
Not every major service offers 2 Factor Authentication, but I suspect that with the Heartbleed leak this will become more commonplace. In my opinion, TFA is a prelude to a new way of identification and authentication for online services. Eventually, this will no longer happen with codes, but with biometric services like your heartbeat or the iris of your eye. Until then, TFA is a great way to better secure your online data. Evan Hahn has made a nice list of services including direct links to the activation page.
Note: TFA gives you better security but it is still not 100% waterproof. Researchers have already circumvented the security of Dropbox. And if you already use TFA, it is wise to regenerate the codes again, because the Heartbleed leak may have an effect on your TFA codes. So stay alert to changes in your accounts.