Deployment
Deployment/registering commands is, in layman's terms, publishing your commands over to Discord's servers. Deploying commands is required; if not done, any metadata about the command, such as command name, description, options, etcetera, will not update, nor will new commands appear.
Discord rate limits the amount of deployments you can have per day to 200.
Global Deployment
Any files in commands/ that end with .(js/ts) will be deployed to all servers.
You can call it by running the following command:
npm run deploy:global
You can remove the GUILD_ID portion of your .env file if you're only going to be using global deployment.
Guild Deployment
Any files in commands/ that end with .gu.(js/ts) will be deployed to the guild id written in your .env file.
You can call it by running the following command:
npm run deploy:guild
You can get a server's guild id by right-clicking on the server's icon and clicking the Copy ID button.
Where to deploy
Guild-based deployment of commands is best suited for development and testing in your own personal server. Once you're satisfied that it's ready, deploy the command globally to publish it to all guilds that your bot is in.
You may wish to have a separate application and token in the Discord Dev Portal for your dev application, to avoid duplication between your guild-based commands and the global deployment.