When you use 2-Step Verification, some apps or devices may be blocked from accessing your Google Account. App Passwords are a way to let the blocked app or device access your Google Account.

Tip: Whenever possible, connect apps to your Google Account by selecting the “Sign in with Google” option available in many apps

What is App Password?

An App Password is a 16-digit passcode that gives a non-Google app or device permission to access your Google Account. App Passwords can only be used with accounts that have 2-Step Verification turned on.

How to Create App Password

Note: If you use 2-Step-Verification and are seeing a “password incorrect” error when trying to access your Google Account, an App Password may solve the problem.

  1. Go to your Google Account.
  2. On the left navigation panel, choose Security.
  3. On the “Signing in to Google” panel, choose App Passwords. If you don’t see this option:
    • 2-Step Verification is not set up for your account.
    • 2-Step Verification is set up for security keys only.
    • Your account is through work, school, or other organization.
    • You’ve turned on Advanced Protection for your account.
  4. At the bottom, choose Select app and choose the app you’re using.
  5. Choose Select device and choose the device you’re using.
  6. Choose Generate.
  7. Follow the instructions to enter the App Password. The App Password is the 16-character code in the yellow bar on your device.
  8. Choose Done.

Most of the time, you’ll only have to enter an App Password once per app or device, so don’t worry about memorizing it.

Credit : Above content is taken from Google Support Forum.