Why does your phone ask "Allow this app?" App permissions explained

Every app on your phone lives in its own sandbox: free to use its own files, but walled off from other apps and from personal things like your location, camera and microphone. To reach those, it has to ask, and you decide.

Tap through a phone simulator on iPhone and Android to see the real choices: while using, only this time, don't allow, always, and precise vs approximate location. Then see what developers must do: declare permissions, ask at the right moment, and keep the app working when you say no.