What is 2-factor authentication?

2-factor authentication adds a second layer of protection during the login process. 

Currently, your Google login is tied to “something you know” (your password). 2-factor authentication adds the second layer of “something you have” (typically your smartphone, a temporary code, or, absent that, a USB security key). You most likely already have experience using 2-factor authentication with an online banking account, so hopefully, enabling it within Google will not be a new experience.