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.
The iPhone 11, iPhone 11 Pro, and iPhone 11 Pro Max introduced Apple's U1 chip with Ultra Wideband (UWB) technology. This feature allows the iPhone to understand its location in relation to other UWB devices, providing what Apple calls "GPS at the scale of your living room". For example, AirDrop knows when you're pointing your iPhone at another iPhone to share content between devices.
You may have photos in your camera roll that you would rather others not see, because they are simply private - whether they are embarrassing, compromising, have private data like passwords in them or otherwise. You probably want to keep them out of sight of somebody who might be browsing your camera roll, whether it is someone who stole your phone or simply a friend you handed it to to check out some pics. iOS offers a way to hide photos but surprisingly doesn't let you put them in a password protected album.