This tutorial demonstrates how to add a camera overlay to a screen-share feed and stream that as a single video track via the Agora SDK, which helps deliver a more seamless and reliable presentation experience in a video calling application. The project setup includes creating an HTML file, sourcing the Agora Web SDK using the CDN link, and initializing a variable to store the App ID generated from the Agora console. The implementation involves setting up AgoraRTC, building a basic user interface, and implementing video multiplexing. Testing is done by starting a web server and inputting the channel name and username, allowing for any needed permissions and selecting which screen to share.