Two-Steps Verification is also known as two-factors authentication, which is a process of adding an extra layer of security to your account. Two-Steps Verification requires something you know (your login password) and something you have (a mobile to receive the code). This will provide more security to your email, since the “authentication code” is generated continuously. Google, for example, provides two-steps verification either via a text message to your phone or via the “Google Authenticator” application.
Google authenticator is a mobile application that generate one-time password every 90 seconds. This application will allow you to generate the two-steps verification codes on your smartphone (network connection is not required).
Remember: Google authenticator can be used to generate verification codes instantly to sign in to your Google application accounts; along with the ability to implement one-time passcode generators for several mobile platforms.
Note: the services of the two-steps verification is implemented via the Time-based One-time Password Algorithm (TOTP) and HMAC-based One-time Password Algorithm (HOTP).
This link provides more information about two-steps verification and other alternative techniques to access your email.
More information about how to setup Google Authenticator.