Kotlin
In plain terms
A modern JVM language and Google's preferred choice for Android.
Going deeper
Kotlin is concise, null-safe, and fully interoperable with Java, fixing many of Java's rough edges. It also targets JavaScript and native.
Under the hood
Null safety in the type system, coroutines for async, and extension functions make it expressive; it runs anywhere the JVM does.
Examples
Android apps, Spring backends, Kotlin Multiplatform, Gradle build scripts.
Think of it like...
Like a renovated version of a solid old house: same foundation (JVM), far more comfortable to live in.