# Custom Commands and Functions

* You can define your own [commands](/2.4/using-yarnspinner-with-rust/creating-commands-functions/creating-commands.md), which allow the scripts you write in Yarn Spinner to control parts of the game that you've built.
* [Functions](/2.4/using-yarnspinner-with-rust/creating-commands-functions/creating-functions.md) are units of code that Yarn scripts can call to receive a value. In addition to the [built-in functions](/2.4/getting-started/writing-in-yarn/functions.md#built-in-functions) that come with Yarn Spinner, you can create your own.


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