Specifically the company is promoting support for CBS, ESPN, and Disney XD; however, there may be other apps that are supported.
To use the feature just tell Siri to 'Watch ESPN' or 'Watch CBS Live'. Of course, if a subscription is required you will need one to watch the live stream.
Apple is also highlighting Dictation, Bluetooth keyboard support, Folders, Live Photos, and Siri app search as "What's New". These features came as part of the tvOS 9.2 update.