Overview (Groovy 2.5.14)

Packages
Package	Description
groovy.text	Contains the text processing utilities including templating APIs and default implementations.
groovy.text.markup	Contains a template engine facilitating generation of XML-like markup with optional type checking.

Groovy - An extensible multi-paradigm language for the JVM Platform
(GroovyDoc for Groovy and Java classes)

Groovy...

is an extensible and multi-paradigm language for the Java Virtual Machine
makes modern programming features available to Java developers with almost-zero learning curve
has a dynamic nature like Python and Ruby, which means that it is very powerful, easy to learn, and productive
optionally has static typing like Java and Kotlin, which makes it fast and provides extra type checking when desired
has first-class functional, stream processing and immutability support, meaning that it offers features similar to Scala and can offer many advantages when working in parallel processing or clustered environments
supports Domain-Specific Languages and other compact syntax so your code becomes easy to read and maintain
makes writing shell and build scripts easy with its powerful processing primitives, OO abilities and an Ant DSL
increases developer productivity by reducing scaffolding code when developing web, GUI, database or console applications
simplifies testing by supporting unit testing and mocking out-of-the-box
compiles straight to Java bytecode so you can use it anywhere you can use Java; it seamlessly integrates with all existing Java objects and libraries