What is this advertising ID by google from the 1st August 2014 ?

I recently got mail from my airpush ad network asking me to update to the latest sdk so that it is compatible for google Advertising ID ? which i dont have much clue abt . i have few doubts , do i have to update all my apps which already exist on play store for this advertising ID or only for the new apps that i will publish should have this advertising ID ? some help wud be appreciated :slight_smile:


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