They collect data on the type of device you’re using, your exact GPS coordinates, even your IP address, and in many cases an ID code that can be used to triangulate your behavior across apps and across devices in order to get a fuller picture of who you are online, how you shop, and then sell those insights to fourth-party companies. These third-party companies not only love to know info that you’ve explicitly given the app, they often track how many times a day you open the app, how long you’re on each time, what ads you’ve clicked on before and when those clicks turn into you actually buying something. Cookies, software development kits, web beacons – these are all types of technologies that companies that specialize in mining data can use to mine your data.