docs: add utility process info to tutorial docs (#36074)

docs/tutorial/process-model.md

@@ -214,8 +214,25 @@ This feature is incredibly useful for two main purposes:
   URL, you can add custom properties onto the renderer's `window` global that can
   be used for desktop-only logic on the web client's side.
 
+## The utility process
+
+Each Electron app can spawn multiple child processes from the main process using
+the [UtilityProcess][] API. The utility process runs in a Node.js environment,
+meaning it has the ability to `require` modules and use all of Node.js APIs.
+The utility process can be used to host for example: untrusted services,
+CPU intensive tasks or crash prone components which would have previously
+been hosted in the main process or process spawned with Node.js [`child_process.fork`][] API.
+The primary difference between the utility process and process spawned by Node.js
+child_process module is that the utility process can establish a communication
+channel with a renderer process using [`MessagePort`][]s. An Electron app can
+always prefer the [UtilityProcess][] API over Node.js [`child_process.fork`][] API when
+there is need to fork a child process from the main process.
+
 [window-mdn]: https://developer.mozilla.org/en-US/docs/Web/API/Window
+[`MessagePort`]: https://developer.mozilla.org/en-US/docs/Web/API/MessagePort
+[`child_process.fork`]: https://nodejs.org/dist/latest-v16.x/docs/api/child_process.html#child_processforkmodulepath-args-options
 [context-isolation]: ./context-isolation.md
 [context-bridge]: ../api/context-bridge.md
 [ipcrenderer]: ../api/ipc-renderer.md
+[UtilityProcess]: ../api/utility-process.md
 [tutorial]: ./tutorial-1-prerequisites.md