The short answer
They share a name and almost nothing else. An app directory (HubSpot, Slack, Freshworks) is a discovery surface for that platform's existing customers, so it drives trials and stickiness rather than large deals. An app store (Shopify) can be a genuine business with revenue share and its own economics, but you live under their review and policy rules. A cloud marketplace (AWS, Azure, Google) is procurement plumbing for enterprise deals, not a discovery channel, and treating it as marketing will disappoint you. Pick based on where your buyer already spends money, and give the listing an owner rather than treating it as a one time launch task.