The document discusses The Ruby Racer, which embeds the V8 JavaScript interpreter into the Ruby process. This allows JavaScript code to be evaluated from Ruby, and for Ruby code and objects to be accessed from JavaScript. It enables features like headless JavaScript unit testing, tapping into Node.js utilities, and allowing client-side and server-side code sharing through templating, validation and business logic. Challenges include garbage collection across languages, but the technology aims to be robust, secure, efficient and cross-platform in the future.