There are different advertising IDs: web cookies, IDFA (Identifier for Advertising) on iOS, and AAID (Google Advertising ID) for Android. They are a way of recognizing an individual user to establish an audience profile and target or retarget the user.
Advertising ID
An advertising ID is an individual identification in the digital advertising context. Only advertisers or advertising solutions can access this ID, which is a way of identifying users while retaining anonymity.