The interaction comes from when you touch the surface, which breaks the lineof sight of the laser and is recognized as a touch just as if you might touch the trackpad on an Apple Macbook.
Finding a lot of sources of information from diverse lines of thought on economics and having a better lineof information on the Reagan 1986 tax legislation as it developed than most, peripherial, but almost daily interaction with the bank closings and later the RTC, gave me a whole different view.