I don't know if you tried reading The Swift Programming Language book ( https://docs.swift.org/swift-book/LanguageGuide/TheBasics.ht... ). It's a fairly quick read and has brief explanations with simple examples. You can skip some sections if you have prior programming experience, but if you're confused about Swift's function arguments, you may want to skim even the basics since a few things like control flow (e.g. the switch statement) are unique compared to C/C++/Java/C#.