Packaging is basically getting all translations together in the original format of your documents. As in some cases or with large files, this may take longer than normal (more than 10 seconds), this method is asynchronous by default. It will return a package key to let you track packaging status. When packaging is "complete", you can make a download call to download your translations.
If you provided a language code, only that language will be ready to download when the packaging status is "complete".
For supported languages, see the "Supported languages" section.
Package is how you track your project's packaging process. With this key, you can make a call to /project/:id/package/check and see the status of packaging.