Since “two factor authentication” just means “a second something is necessary to get in”, this answer depends upon the particular set-up. In the most common case, a numeric code is shown on your phone, tablet or other device. This code could be sent via an SMS, but this depends on the mobile phone network working, and is technically easy to hijack (and so is not recommended by security professionals). So, this plugin does not uses that method. Instead, it uses a standard mathematical algorithm to generate codes that are only valid once each, or for only for 30 seconds (depending on which algorithm you choose). Your phone or tablet can know the code after it has been set up once (often, by just scanning a bar-code off the screen).
Posted in: Two Factor Authentication