The Dojo is Urbit's command-line application that processes system commands and returns output. It also runs Hoon and Nock code, making it a good place to play around with those languages.
The other default command-line app is Chat. To switch between Dojo and Chat press Ctrl-X. The Dojo is the first thing you encounter after successfully booting your ship.
- Hoon Tutorial Lesson 1.1: Setup: A great way to get started with using Hoon in the Dojo.