A bong is also a water pipe; however, it is more of a filtration apparatus, which as opposed to being primarily made to smoke tobacco, is actually used to smoke cannabis, or other herbs.
A bong works using very simple mechanics - gas flows from its lower part to its upper part, where it enters the users mouth and then the lungs.
Structurally the hookah and bong are quite different, despite them being used for nearly the same thing. Bongs are much smaller and can be easily constructed. All you need to construct a bong is an air and water tight device, after which you need to add a bowl and a stem to it.
Bongs have been around for quite some time, being used in Thailand and parts of Africa for a number of centuries now. The earliest use of the word bong, or words used to describe what a bong, is were published in 1944.
A hookah is a middle eastern apparatus, which is used to smoke flavored tobacco. It has a pipe attached to a water base, and it uses coal and water to produce smoke and water vapors, which help enhance the flavor.