This tutorial explains how to add manual track subscriptions to a Daily call object, allowing for larger calls with better performance and quality. It introduces features such as staged and subscribed participant IDs, updating the Daily call object, playing and pausing tracks based on participant events, and rendering subscribed tracks in a paginated video chat app. The implementation uses Daily's publish-subscribe model and manual track subscriptions to support larger call sizes, deliver better call quality, and preserve participants' CPU.