Urbit ships by default with Landscape, a web-based interface for managing your ship and the software installed on it, and launching other web-based applications. However, there are many ways to interact with your Urbit.
There's EScape, a fork of Groups that also has an accompanying mobile application. Scene and the (soon to be released) Realm offer native desktop window managers for your urbit. Lastly, there's the Dojo CLI interface for developers