Autopilot: How does the "Sign in with Google" option work?

When you visit the login page you'll notice that there are two options available:

• sign in with Google; and
• sign in with a regular Autopilot account.

Regardless of whether or not you signed up with Google, if the email address you used to create your Autopilot account is the same as your Google email address, then you can use the "Sign in with Google" option to login to Autopilot.