iOS

A View Controller helps manage the app interface along with responding to user input, whereas a View does the actual display of UI elements like labels or buttons.   

Xcode is an integrated development environment (IDE) built by Apple runs on macOS and is used to develop iOS apps. It consists of a code editor, simulator, and more.

UIKit is the framework that gives you the elements necessary to build and manage the interfaces of iOS apps—views, controls, and animations.  

The delegate design pattern enables one object to send messages to another when specific events occur to manage the actions of users or system occurrences.

Core Data is modeled around data management in any iOS application and provides an object-oriented approach to the modeling, storage, and management of any application data. 

An iOS application can have four major states: Not Running, Inactive, Active, and Background state. All the transitions between the states are based on user interaction and system events.

An iOS application can have four major states: Not Running, Inactive, Active, and Background state. All the transitions between the states are based on user interaction and system events.

Swift is Apple's programming language developed for iOS and macOS development; it is fast, safe, and easier to use than Objective-C.

Strong ones keep an instance alive; weak ones avoid retaining cycles and do not own the objects; unowned ones do the same but expect that the object will not be nil after initialization.

Auto Layout is a mechanism for responsive UI design in an iOS application, permitting the specification of the layout via constraints while taking care to ensure the UI works on different screen sizes.