The document discusses JRuby, which is a Java implementation of the Ruby programming language. JRuby allows Ruby code to leverage Java libraries and infrastructure and run on the Java Virtual Machine. It provides benefits like running the same code on all platforms and leveraging existing Java skills and tools. However, it also has drawbacks like a larger memory footprint compared to other Ruby implementations. The document provides examples of using JRuby for web applications, system integration projects, and describes some organizations that use JRuby in production.