what is kotlin data
Kotlin is a new language (sometimes referred to as Swift for Android), developed by the JetBrains team, and is now in its 1.0.2 version. What makes it useful in Android development is that it compiles to JVM bytecode, and can be also compiled to JavaScript. It is fully compatible with Java, and Kotlin code can be simply converted to Java code and vice versa (there is a plugin from JetBrains). That means Kotlin can use any framework, library etc. written in Java. On Android, it integrates by Gradle.
We frequently create a class to do nothing but hold data. In such a class some standard functionality is often mechanically derivable from the data. In Kotlin, this is called a data class and is marked as data: data class User(val name: String, val age: Int)