# Base

The `%base` desk is the distribution of Urbit OS that lives on your server. It contains the Urbit kernel, Arvo, the Hoon standard library, type definitions, and several libraries and other tools that make Urbit work. We cover Arvo in the [kernel](https://docs.urbit.org/urbit-os/kernel) section. This section contains documentation for everything else in the `%base` desk.

* [Hood](https://docs.urbit.org/urbit-os/base/hood) - Developer documentation of the `%hood` system app and its three sub-modules: `%drum`, `%helm` and `%kiln`.
* [Threads](https://docs.urbit.org/urbit-os/base/threads) - How to use threads and the `%base` desk's strandio library.