Lightning tends to be long and skinny.
The central ray of electricity in a lightning bolt can travel more than 2 miles (3 kilometers), whether down toward Earth, horizontally, or upward into the higher atmosphere.
The bolt is usually only 6 inches (15 centimeters) in diameter, and often much less. The surrounding brightness of the flash extends further, but technically it is not part of the lightning.
It comes from the heating of air particles around the lightning bolt.