This tutorial provides an overview of how to add screen sharing functionality to a browser-based video chat application built with JavaScript and the Twilio Programmable Video API. The application requires Python 3.6 or newer, a free or paid Twilio account, and a compatible web browser. To start screen sharing, users are prompted to select what they would like to share, and once a selection is made, the video track is created and published to the call. The tutorial also covers layout improvements, such as adding a "Share Screen" button next to the "Join call" button, and assigning a CSS class to the participant's name to make it easier to add background color. Additionally, the tutorial explains how to implement a full-screen feature that makes any video track full-screen by clicking on it. The screen sharing functionality is complete once all the changes are implemented, including adding click event handlers to all tracks, zooming in and out when clicking on a track, and handling track publication and unsubscription.