Darwin is a community-based ChatBot. You basically just talk to it, just like Siri or Cortana. While it serves no practical functionality at the moment, we are constantly working on it. Darwin works on all platforms, as long as your browser isn't from the Cretaceous period.
Making a chatbot is tedious work. You need to preprogram thousands, if not millions of responses all by yourself. This is why Darwin is community-based. If you say something that Darwin doesn't understand, you can tell it what to say, and it will add your suggestion to it's language database.