You may be finding the GAID (Google Advertising ID) of your Android device. Its role is the same as IDFA (IDentifier For Advertising) for iOS devices.

This app provides with the AAID of your Android device. You can also easily copy and share it.

AAID definition from https://support.google.com/googleplay/android-developer/answer/6048248?hl=en.
▷The advertising ID is a unique, user ID for advertising, provided by Google Play services. It gives users better controls and provides developers with a simple, standard system to continue to monetize their apps. It enables users to reset their identifier or opt out of personalized ads (formerly known as interest-based ads) within Google Play apps.