What impact does a domestic business have on the economy? I know it increases the GDP of the country, but other than that? Is it just a redistribution of money within the country's walls? [Whereas an international business (any business that exports or provides services to foreign countries) actually brings in new sources of money, actually creating new jobs.]

The redistribution in and of itself is value. When you have more money circulating, that means more people are consuming, which ends in an overall higher quality of life. This is where the value lies.

Along the same lines, but a bit more concrete, is harvesting raw materials. More materials are harvested, more is developed, quality of life is increased.