Shopify's CEO says Amazon isn't a competitor, but Amazon's CEO says it is. Here's what experts say the real relationship is. (AMZN, SHOP)

· Amazon CEO Jeff Bezos wrote in his statement to the antitrust House committee last week that Shopify is a new competitor.
· Shopify CEO Tobi Lutke, however, said Amazon is not a "direct competitor" during the company's earnings call last week.
· E-commerce experts say they're "indirect" competitors that effectively play in...