alt Hacker NewsAstro component is your page's entry point. It's similar to React server component. The typical flow is to fetch data in it, and pass the data to client component written in React or whatever. You can also have pages that are Astro only, without any front-end framework.
Yeah, I know, but since by default the front-end islands are server-rendered with no hydration the lines are blurred between what you would use an .astro component for, and just using for example react.
Personally I only ever use .astro components if I'm 100% sure I will never need any client side interactivity, otherwise it's just easier to ignore them.