The Track Subscriptions API is a new REST API available for Group Rooms. It allows developers to define which participants are subscribed to which tracks. Currently Group Rooms use a "subscribe-to-all" model meaning that participants are subscribed automatically to all the tracks published to the Room. With this new API, developers can now set, in a dynamic and configurable way, the desired communication topology: one-to-many (e.g. presentations where only one participant publishes and the rest only receive), some-to-many (e.g. collaborative presentations where some participants talk and the talk is published to the rest), whisperers (e.g. participants that can listen/view to all but can only be listened/viewed by some), and more.
By default, the Track Subscription API is deactivated. To implement this functionality for your applications, you will need to use the API to set subscribe rules.