The attributes apple uses is listed in that very link.
The key to segments is ensuring that the attributes give you enough entropy.
The key to segments is ensuring that the attributes give you enough entropy.
In Apple's world, Apple owns the supply side ad surfaces, Apple maintains the segmentation and mapping, and Apple mediates the demand side.
What does an advertiser see? Pretty much nothing.
You can learn more about how safari protects you by reading these blog posts.