You can log into Topicbox without a password: we send a one time code to your email address that you use to log in with.
You can log into Topicbox with a password. Useful if you don't have access to your email account when you connect.
You can log into Topicbox with two-step verification (also known as two-factor authentication, or 2FA). This is where you use a password AND a code generated by a security device (either an app on your phone or a separate physical device that plugs into your computer).