When getting ready to assess iOS apps, it is important to understand application states. There are various app states in iOS. Apple allows only one state at a time. These states changes according to user or system actions.
For example, suppose you press the Home key and a text message (SMS) comes in, the currently running app changes its state to the background.
The following are the different states in iOS:
Not running: The app will be in this state before it is started and after it is terminated or aborted.
Inactive: An app in the inactive state is still running in the foreground but will not receive any events or alerts. For example, if you are browsing a website in Safari and receive an SMS and switch over to the SMS app, Safari is in the inactive state until it is reopened.
Active: When an app icon is clicked, it goes into the active state and will run in the foreground and actively receive events.