Overview#Identifier for Advertisers (IDFA) is an Advertising ID and is a random device Unique Identifier assigned by Apple to a user’s device.
Identifier for Advertisers reveals no personal information. Instead, it’s used for tracking and identifying a user, which then allows advertisers to access aggregated data which can be used to discover information – such as which in-app events they trigger.
Identifier for Advertisers can also identify users when they interact with a mobile advertising campaign, provided the channel offers IDFA tracking and that the advertiser tracks users who interact with adverts successfully. If this occurs the IDFA can pickup whether specific users click an advert for payment and attribution purposes.
Users can opt out of all remarketing by enabling a device setting called "Limit Ad Tracking" (LAT), which restricts advertisers from using the IDFA for behavioral advertising.*
Identifier for Advertisers is used in Real-Time Bidding