Update dom without reloading the page

I understand how to have a twig calling a function to receive content onPageLoad. However I am wondering if it is possible to call a function and return from user input without refreshing the entire page.
in other words: dynamic content

I have one word for you - JavaScript

I have two more: AJAX and PJAX. Really any reactive JavaScript framework; Vue, React, etc.

It's JavaScript in any case :)