swift.org
docs.swift.org/basics
docs.swift.org/reference
developer.apple.com/swift
Swift is a general-purpose programming language built using a modern approach to safety, performance, and software design patterns. The goal of the Swift project is to create the best available language for uses ranging from systems programming, to mobile and desktop apps, scaling up to cloud services.
swift.org/package-manager
developer.apple.com/swift-packages
github.com/apple/swift-package-manager
The Swift Package Manager is a tool for managing the distribution of Swift code. It’s integrated with the Swift build system to automate the process of downloading, compiling, and linking dependencies.
Swift packages are reusable components of Swift, Objective-C, Objective-C++, C, or C++ code that developers can use in their projects. They bundle source files, binaries, and resources in a way that’s easy to use in your app’s project.
SwiftUI is a modern way to declare user interfaces for any Apple platform. SwiftUI provides views, controls, and layout structures for declaring the app’s user interface.
developer.apple.com/foundation
The Foundation framework provides a base layer of functionality for apps and frameworks, including data storage and persistence, text processing, date and time calculations, sorting and filtering, and networking. The classes, protocols, and data types defined by Foundation are used throughout the macOS, iOS, watchOS, and tvOS SDKs.