Kotlin has become quite popular since Google announced it is supporting the programming language at the Google I/O 2017 conference.
Kotlin helps you avoid common programming language mistakes such as Null Pointer Exceptions because of the built-in features that improve the quality of app development. Another advantage is the fact that Kotlin is 100% interoperable with Java and requires writing less boilerplate code which in turn saves time in testing and maintenance.
Kotlin runs on Java Virtual Machine, which is widely used for developing Android apps.
Here is a simple guide to build your first app with Kotlin.