Apple has tightened its rules for advertisers who are trying to track users on their iPhones. The company wants advertisers to universally adopt its IDFA (or IFA) system for tracking. IDFA stands for "identifier for advertisers."
The move will likely increase the number of people whose iPhone activity is tracked by advertisers, because in newer versions of Apple's iPhone operating system (iOS 6 and later), the privacy controls are situated in the "General" menu within Settings, and not in the "Privacy" menu. Tracking is on by default. Users must choose to switch it off if they do not want to be tracked. (Here are some instructions for switching off tracking.)
IDFA is similar to a cookie — it allows advertisers to know that a specific iPhone user is looking at a specific publication and can serve an ad targeting that user.
The tracking is anonymous. It doesn't show advertisers any personally identifying information. But it does show them what you're doing and what you're interested in.
SEE ALSO: Apple Has Quietly Started Tracking iPhone Users Again, And It's Tricky To Opt Out