Kotlin is a statically-typed programming language developed by JetBrains, a software development company based in Russia. It is designed to be a modern and concise language that can be used to develop a wide range of applications, including Android apps, server-side applications, and desktop applications.

Kotlin is fully interoperable with Java, which means that existing Java code can be used within Kotlin projects and vice versa. This compatibility with Java has made Kotlin increasingly popular for Android app development, as it offers a more expressive and concise syntax compared to Java.