How to correctly render multiple apps on the main page

So I'm currently learning to use Django, and I'm wondering how to correctly split up parts of the functionality while still displaying it on the main page.

For example, I want the header + navigation, a calendar and recent blog articles on the main index page.
On the view article page I'd for example have the header + nav, the calendar and a single article with a comment section.

Now reading the tutorials, if I understand them correctly, I'd split the functionality in a header app, a calendar app and the blog app itself while glueing it together with a core app.

But what I don't understand is how to render apps/other views in the main app. All the ways I found only specify templates itself or look very hacky, so apparently that doesn't seem to be the common way to go.