A GROOVY file is a source code file written in the Groovy programming language. Code written inside a GROOVY file is similar to the object-oriented language Java, that makes it easy for design and development of applications. A GROOVY file is compiled to Java virtual machine (JVM) bytecode and is compatible with other Java code and libraries.
GROOVY File Format - More Information
GROOVY files contain source code written in Groovy syntax. It can contain code that can be used as both a programming language as well as a scripting languages for the Java Platform. Groovy language has the features similar to those of Python, Ruby, and Smalltalk.