UIKit is a framework provided by Apple for building user interfaces in iOS and tvOS applications. It offers a wide range of pre-built components, such as buttons, labels, and text fields, which developers can use to create visually appealing and interactive apps. With UIKit, developers can manage the app's layout, handle user interactions, and animate elements on the screen. It supports both touch and gesture-based inputs, making it easier to create responsive applications that work seamlessly on various devices, including iPhones and iPads.