Unlike Apache Ant and Apache Maven which used xml, Gradle uses a Groovy/Kotlin based script file. (See example)
Gradle works on JVM.
Gradle was designed for multi-project builds, which can grow to be large. It operates based on a series of build tasks that can run serially or in parallel. Incremental builds are supported by determining the parts of the build tree that are already up to date; any task dependent only on those parts does not need to be re-executed. It also supports caching of build components, potentially across a shared network using the Gradle Build Cache.
Most IDE goes with built-in Gradle. But you can install it standalone.