Google prompt makes two-step verification sign-ins easier for Android and iOS Google users
New Google prompt makes it easier to complete the second step of a two-step verification
By going to My Account and then Sign-in & Security > Signing in to Google > 2-Step Verification, you can select any of the options you'd prefer for the second step of the verification process. Google's blog appears to call this feature Google prompt, and users must have a data connection for it to work. In addition, Security Keys and Google prompt cannot be both enabled at the same time.
The update will hit all Android users over the next three days through a Google Play Services update, and iOS users will need to have the Google Search app installed to use Google prompt.
source: Google via 9to5Google
Things that are NOT allowed: