Yep they probably tick when the engine is running, most if not all injectors do. Nothing to be concerned about, they all tick.
The ticking means there working, well its more or less the injector opening and closing, thats the ticking. There spring loaded inside, and its the plunger inside of the injector that moved up and down to allow fuel into the cylinder, I think thats where the ticking occurs!
Plunder opens and closes according to the signals from the ECU.
The plugs to the injectors do supply power to the injectors as well as signals from the ECU about how much fuel to spray in to the cylinder, when and in what order. Those signals are made up from various other things such as airflow (AFM or MAP), throttle position (TPS), coolant temperature sensor, voltage sensor, engine speed sensor etc, etc..
Sensors do all the reading (sensing), and the ECU does the calibrating. I think thats the correct wording!