Some app's listen for sound we cannot hear but the TV or other devices can produce. That can be used to target people/regions/etc for various things based on search history. (For example, a commercial can be embedded with that sound for a specific city/state/region/etc then the app on your phone can be used target you almost specifically). The advertising world is very much like the creepy shit you see in tv shows with the government secretly watching you. It can even be apps that you would never expect like a downloaded calculator app or something. Also, there is so much instrumentation built into most big apps that it gives you a huge amount of data. From my work this is a small amount that I know about you and your phone just from installing the companies app. Approximate location (exact if you have it turned on). What patch level your phone is. If you have rooted or jailbroken your phone. What phone it is specifically (manufacture, generation, screen size, etc). If you use something like touchID Anything you do in the app (literally anything, I can tell what button you pressed in the app when you used it and if it was fast or slow to respond). Cell network provider(s). Etc...