How Turbo Frames update part of a page inline, no JS required, no full reload:
"The JavaScript in Turbo Frames looks at any links you click or forms you submit inside that Turbo Frame, sends that over to Rails, processes it like normal, but looks in the response for the matching Turbo Frame. If it has another Turbo Frame with the same ID, it takes the content from that part and returns that, only updating the current page with that little snippet.
To make this work, our subscribers create action will render a template with a turbo frame tag with the ID of subscribe form. Put in my email address, hit subscribe. It just updates this. It didn't change the URL. That HTML was just grabbed out of the request."