"Authy is a simple API to add two-factor authentication to your website or app"

Two-factor auth is a thing where when you log in to something, you also get a text message, or open an app on your smartphone, and type that into the app you're trying to log into. The purpose of this is that even if someone figures out your password, they can't get access to your account, because they don't have the 2nd form of auth (hence two-factor.)

It's a way to add two-factor authentication to your website or app. Instead of having people log in with just username and password, they'll also have to enter a code. They get the code from the Authy app on their phone.

(PS I'm not affiliated with Authy, just trying to be helpful.)