The company descries Kotlin as “a pragmatic programming language for JVM and Android that combines [object oriented] and functional features and is focused on interoperability, safety, clarity and tooling support.” The pragmatism is meant to suggest Kotlin will be built correctly rather than quickly.
General purpose, Kotlin works everywhere Java does, and uses Maven and Gradle for its package management/build system.
Though Jetbrains created Kotlin, it’s an open source language.
According to Jetbrains, Kotlin has been production ready for some time; this 1.0 release has been some time in the making, with the team dedicated to getting the design principles right (pragmatic!) to better support backwards compatibility.
If you want to give Kotlin a test run, there’s a web-based portal where you can give it a try. Android Studio and Eclipse both have plugins for Kotlin support, and the IntelliJ IDEA IDE fully supports the language.