A goodwill repair is something the manufacturer decides to repair even though they aren't obligated to. It counts as opex instead of cost of revenue like a warranty repair. It might also not count towards repair attempts for lemon laws.

The article alleges that Tesla is repairing issues that are covered under warranty as "goodwill repairs" instead to help the balance sheet and circumvent lemon laws. As an owner, you might not care too much since the issue is getting repaired either way.