The Touch object detects input from touchscreen devices like iPhones, iPads, Android and Windows 8 devices. Touchscreens for desktop computers are also available, but these are rare compared to mobiles, so generally the Touch object is used in anticipation of input on a mobile device.
The Touch object also provides input from the accelerometer (motion) and inclinometer (tilt/compass direction) if the device supports them.
It is best to support touch input wherever possible. On the modern web many users are now browsing on mobile devices with touch input only and no mouse or keyboard. If your game does not support touch controls, many users will be unable to play your game at all. For a guide on how to implement on-screen touch controls, see the tutorial on Touch controls.
For a number of examples of using Touch input, search for Touch in the Start dialog.
The Touch object supports multi-touch. This is most useful with the On touched object and Is touching object conditions, which can for example detect if multiple on-screen touch controls are being used. This is sufficient for many games.
For more advanced uses, the TouchID, XForID and YForID expressions can be used to track individual touches for different purposes. Each touch has a unique ID (which is an arbitrary number), and can be accessed using the TouchID expression in an event like On any touch start. The touch ID can then be stored in a variable and tracked using the XForID and YForID expressions. Finally comparing the TouchID in On any touch end indicates when that touch has been released.
The Touch object has no actions.