The data stored on your iPhone is a valuable commodity to both businesses and governments, and if you don't maintain constant vigilance to protect it, it can leak out in any number of ways, including through unscrupulous apps. Aside from tracking your location and purchasing habits among other metrics, apps can also use your iPhone's microphone and camera, potentially allowing them to invade your privacy in the worst possible way - by listening to and watching you. Obviously you want some apps to have access, but there are plenty that don't need it yet ask for it anyway.
Some iPhone owners are tired of the relentless stream of commentary on social media. If Twitter is taking up too much time, or tweets are getting you down, the service provides an easy way to deactivate your account. Accounts that are accidentally or wrongfully deactivated can be restored within 30 days before they are wiped. For anyone ready to throw in the towel on their twitter handle, accounts can be deleted in a few steps.
Apple devices can use GPS, Bluetooth, cell towers, and Wi-Fi hotspots to determine your location. The iPhone periodically sends location data back to Apple, in an anonymous and encrypted form. This data is used to improve location-based services on everyone's devices, such as displaying real-time traffic or suggesting popular locations. Many apps can use location data in the background, and iOS will periodically notify users when this data is being collected.
The iPhone has included on-board GPS since the second generation iPhone 3G. With the release of iOS 13, Apple added more granular controls over how apps use location data, giving the user more privacy controls. Location data and privacy issues are back in the news lately, with the addition of ultra wideband location tracking to the iPhone 11. Many apps can use location data in the background, from GPS and other sources.
Apple Arcade is Apple's video game service that launched in the fall. A five dollar monthly subscription gets you access to tons of games, which can be quite addictive for youngsters and adults alike as we've seen with the recent Fortnite craze. If you don't want your kid playing games all day long or playing with other people online or making inn-app purchases, Screen Time will let you set these restrictions.