Which feature allows users to control Apple TV using their iPhone or iPad?

The feature that allows users to control Apple TV using their iPhone or iPad is the Apple TV Remote in Control Center. This functionality is built into the iOS operating system, enabling users to easily access the Apple TV Remote through the Control Center on their device. Once opened, the remote interface provides essential controls such as a touchpad for navigation, buttons for play/pause, and an option to enter text, making it a convenient alternative to the physical remote.

Other options do not serve this specific function. Apple Music is primarily for streaming music and does not include controls for Apple TV. AirPlay is a feature for streaming audio and video content to Apple TV but does not provide direct control. The Siri Remote is a physical remote control designed for Apple TV, not a feature that links the iPhone or iPad to control the device. Therefore, the Apple TV Remote in Control Center stands out as the most direct way for iOS users to manage their Apple TVs.