The tutorial covers how to create a sticky header effect in a video call app using only CSS. The code for the sticky header is just two lines of CSS, and it allows the user to keep the video on the page while still being able to consume additional content simultaneously. The tutorial also shows how to shrink the video call UI whenever it sticks to the top of the page, providing more space to read the content below the call. To achieve this, a transition is added in the CSS and JavaScript code, which updates the width property of the video container element when the .scrolled class is applied or removed on scroll.