Memory management in iOS apps is handled using Automatic Reference Counting (ARC). ARC is a feature of the Objective-C language that automatically keeps track of how many references point to a given object, and automatically releases the object when the reference count drops to zero.
For example, consider a simple app that displays a list of contacts. The app will create an array of contact objects when the user opens the app. Each time the user adds or removes a contact, the array of contacts must be updated. To keep track of the contacts, the app will use ARC to create a strong reference to the array. Each time the user adds or removes a contact, the reference count for the array will be updated. When the user closes the app, ARC will automatically release the array and free up the memory it was using.