The above Speedlite EX320 from Canon is a type of flash unit, which is attached to the camera hotshoe.
For digital photography, flash refers to a type of light with the super strong brightness which is needed for illuminating a shooting scene or freezing objects that are quickly moving. There are two types of flashes, in which the first is the light from the flash unit and the second is the electronic unit that actually creates the light.
The color temperature of a flash of light is about 5500k (short for kelvins). The duration of burst of light ranges from 1/1000th to 1/200th of one second
Modern flash light needs to be powered and the power comes from single use flashbulbs. Originally, flammable powder was used to provide the power! You’ll find some various types of flash. Commonly, there is a built-in flash unit in solid digital cameras. And, at times you can find built-in “pop-up” flashes in DSLR cameras. Usually, the pop-up flash is a little bit weak. Therefore, a hot shoe is often available in all DSLR cameras so that you can attach an exterior flashgun to this hot shoe (this accessory is positioned on the camera top panel).
Photographers at the professional level often use independent flash units, referred as to studio lights. You can power these flashes by battery packs or outlets.
You often find a tube with electronic flash and this tube is full of xenon gas. The electrical arc is generated through the process in which high voltage electricity has been discharged. Then, a short flash of light is emitted by this arc. You will find an instruction number that shows the strength of a specific flashgun.