The Presentation API currently allows pages to request a presentation of a newly opened page (given a URL) to a secondary display. This feature allows pages to request a presentation of themselves, and to customize certain aspects of how the page will be mirrored to the secondary display.
This allows websites to mirror what is currently shown in the tab to remote displays. This is simpler than launching a presentation receiver page in a separate browsing context to be displayed (what is currently available in Presentation API), in which the receiver page often doesn't have the same user session state as the controller page. See the explainer for use cases.