This is generally subdivided into 4 different types:
1. A file which you can download, for example an eBook.
2. A text-based product, such as a game key or license code.
3. An online service, like creating a logo for someone.
4. A dynamic delivery which lets you programmatically perform certain actions once a payment is successfully processed. A good example is automatically upgrading someone's account on your forum (or Discord channel)
I've been interested in generating procedural art, and some other similar things and that's been a sticking point.
When that's implemented, the customer will be able to enter any kind of detail you'd like them to (like their username, MAC address, or something else) and we'd pass that info on to you when they successfully check out.
With that, you can then automatically perform actions and deliver the digital product/file.
Our roadmap currently looks something like this: API -> subscriptions -> product embeds -> basket system (so a customer can purchase multiple digital items from the same store)