When you press mod, the JavaScript code that's rendered by those blocks (you can click the javascript tab to see) is sent to our cloud storage. Every few seconds, your private server runs a routine that will... 1) check the cloud storage for any new mods, or any mods that have been updated under your profile 2) load or reload the mod as a script in a Minecraft server profile we have for your Minecraft user. At this point you should see the following text in the Minecraft chat: "mod loaded ([mod name])" We use main as an entry point for the mod, so that the code doesn't just run right when it loads; you get to run it with the book or the /js command. Basically, it's what you do with init. So if you change the function named 'init' to 'main' in your code, you'll avoid a common LearnToMod error.