This is the running Heroku app that you just deployed using the Heroku Button
The app happens to be written in Node.js, but Heroku also supports apps written in Ruby, Python, Java, PHP, Scala and Clojure.
You clicked a Heroku Button.
Heroku Buttons link GitHub repos with minimal application setup information — together these allow Heroku to create an application, fetch the source code, deploy the app, configure its environment and deploy any third party add-on services it may use.
Go back to your Heroku Dashboard. The app page has details on how you can clone the source code to start hacking on it and build the application that you want.