Kotlin is a programming language created by a Czech company called JetBrains. The first official release of Kotlin came only last year, although the language has a history that stretches back to 2010.
Kotlin offers most of the same basic features as Java, but it lets you spend more time on the interesting parts of code, and less on routine matters.
Although it was possible to write Android applications using Kotlin before, Google recently approved it officially as a first-class programming language for Android development.
Jetbrains wrote on their official blog:
Today, at the Google I/O keynote, the Android team announced first-class support for Kotlin. We believe this is a great step for Kotlin, and fantastic news for Android developers as well as the rest of our community. We’re thrilled with the opportunities this opens up.