Electronic Flash Question for the Geeks
 

There was a time when the 'flash' in electronic flash units was a glass tube
filled with an inert gas. A high voltage was applied to the tube to create
the flash. I recently bought a good quality (Nikon SB-800) flash and some
things in the manual lead me to believe it is a different animal. The flash
is described as an 'Insulated Glass Bipolar Transister'. Some of the
instructions refer to 'Start firing' and 'Stop firing'. This leads me to
believe the 'flash' is actually a series of short-duration flashes.

Can some of you electronic folks bring me up to date on this technology?
Thanks for any help.