Kotlin is a programming language developed by JetBrains, the company behind IntelliJ IDEA, a popular Java IDE. Kotlin is fully compatible with Java and is designed to improve upon some of the shortcomings of Java. It is a statically typed language that is concise, expressive, and safe. Kotlin is more expressive than Java, which means that it requires fewer lines of code to accomplish the same tasks. It also has built-in null safety features, which help prevent null pointer exceptions. Additionally, Kotlin can be used for both Android and server-side development. It is officially supported by Google as a first-class language for Android development.