We just learned that when the lightning electricity zaps down or discharges it's called the Return Stroke.
Most of the time when lightning zaps down in a lightning strike it is not just one zap, it is anywhere from 3 to 30!
The flashes are so fast sometimes it looks like a flashing strobe light.
After the first return stroke, the other zaps are called re-strikes.

(from: wikipedia - lightning)
Kid Facts - Blast from the past: Mercury