Before we get to the 7 best free courses that will teach you everything you need to learn about Kotlin, let me tell you what it really is.  It was way back in May 2019 that Google announced something we all had known inside for a long time. Kotlin had become the most popular programming language for Android App Developers. The main advantage that Kotlin has over other programming languages is the fact that it is really simple and concise. It requires less programming, less testing, and less maintenance.  These days, Kotlin has firmly dethroned Java as the go-to programming language for Android app developers. But Kotlin has even bigger goals. It aims to become the preferred programming language for multiple platforms, including iOS.