A piece of code that’s linked to an event that can occur in your app.

Part of the Xcode toolbar that displays messages about the build process and other information.

A UI that automatically adjusts so that it looks good in the context of the available screen space.

To indicate that a class, structure, or enumeration conforms to a protocol.

A set of functions, classes, protocols, and other components that define how pieces of software should interact with each other.

An object in your app (specifically, an instance of the AppDelegate class) that creates the window where your app’s content is drawn and that provides a place to respond to state transitions within the app.

An object in your app that’s responsible for managing the life cycle of the app, communicating with its delegate, the app delegate, during state transitions within the app.

A value you pass in to a function, method, or initializer to satisfy one of its parameters.

A data type that stores multiple values of the same type in an ordered list.

An inspector that you use to customize visual attributes of a UI element in a storyboard.