For example, a Javascript+HTML game might be itself considered content, but within the game the game elements and controls (mouse, player characters, NPCs, keyboard bindings) wouldn't be considered content, whereas images and dialog text might reasonably considered content again.

One way of understanding the meaning of a dubious phrase is examining its use in context. For example, one of the pages of the Astro docs begins as follows:

"Astro is the web framework for building content-driven websites like blogs, marketing, and e-commerce" [0]

Ok; so we have our prototypes — or, as Jason Miller would call them, holotypes — of the mysterious "content-driven websites". They are blogs, marketing sites, or e-commerce sites.

Another way of understanding the meaning of a confusing phrase is hearing the distinction explained by the creator of the framework. In early podcasts, when Astro was still mostly unknown, Fred Schott explained that it was not intended for building something like Figma, or Photoshop, or Facebook, or Youtube; but rather something like blogs or magazines; although primarily he was probably targeting the creators of e-commerce websites, because those were the ones that could bring in money.

[0] https://docs.astro.build/en/concepts/why-astro/