An internship is on the job training – it used to be called work experience when I was younger.
The logic behind being an intern is that you get the necessary experience in whatever (usually white collar) job you’ve got the internship in and can then use that experience to get a paid job in the future.
Some internships are paid but a lot aren’t.
If you’re paying out more for your internet marketing than you’re bringing in. Or if you’re getting paid well below the minimum wage for your internet marketing endeavours then, at best, you’re an intern in your own business.