Interactivity to me usually means something to do with a computer and more specifically, games. This would be earliest form of computer games which only needed a click or two like web browser games. These basic actions are on the lowest of interactivity scale.
The medium level of interactivity would mean a more sophisticated action performed by the user to the technology.Using games again, this would involve more than just a click – the graphics itself would be much, much more advanced which might even need a better graphic card to view. Actions might include keyboard and mouse combination or even with an external joystick plugged in.
The current high level of interactivity is the touch screen type of thing which includes ATM, tablet etcetera because of how the “screen” was made to be able to sense pressure and relay the information the user asked.
But technology is not static, they change over time so high level interactivity can be interpreted as future technologies. Let’s take the games example again, right now, we have simple mouse-keyboard computer games, then we have some sort of touch screen. Years later, we may even have virtual worlds/games where everyone wears a headset and emerge themselves into the game as they experience it like real life. Currently there is no such games but there have been many concepts like that were made, such as, the famous (at list to Japan) .Hack series.