A moving thunderstorm gathers a pool of positively charged particles along the ground that travel with the storm. As the differences in charge continue to increase, positively charged particles rise up taller objects such as trees, houses, and telephone poles.
The negatively charged area in the storm will send out a charge toward the ground called a stepped or downward leader. When the downward leader gets close to the ground it is attracted by positively charged objects and a channel develops. You see the electrical transfer in this channel as lightning. There may be several return strokes of electricity within the established channel that is seen as flickering lightning.
The best lightning protection system will produce an upward leader that is stronger than other nearby objects at an optimum time.
The lightning protection system must conduct the lightning discharge through a continuous low impedance path to ground.