What is two-factor authentication? According to Wikipedia:
Two-factor authentication (TFA, T-FA or 2FA) is an approach to authentication which requires the presentation of two or more of the three authentication factors: “something the user knows”, “something the user has”, and “something the user is”.
There are three generally recognized factors for authentication: something you know (such as a password), something you have (such as a hardware token or cell phone), and something you are (such as your fingerprint). Two-factor authentication requires the system to use two of these.
Why should you care? For extra security, having two or more of the mentioned security factors for authentication helps to make your login more secure.
For email purposes, currently only Google’s Gmail service is the only major webmail provider that offers this option, although Microsoft Hotmail’s forum moderators recently thought differently. An interesting article by Fahmida Y. Rashid outlines the questions asked of the support forum regarding Microsoft Hotmail’s authentication with some surprising responses. It only took 3 weeks for an informed response to be posted.
So now you know what two-factor authentication is, shock and awe your friends!