Quickly described, bongs are the same thing as waterpipes but without hoses. With a regular waterpipe you slowly suck the smoke trough the hose and the water. But,
with a bong the smoke will pass the water in one bang because of pressure difference, thus this is why bongs are called bong !
Asian are the ones to thank for the shape of these water pipe ( bongs ). People ( especially in amsterdam ) generaly use bongs to smoke what is called today soft drugs which is know as : marijuana /cannabis !
On top of each bongs you'll find a bowl in which you place your smoking herbs. The smoke passes through the liquid ( usualy water ) before getting to the mouth. Some of carcinogens like tar are filtered . The water in the bong also cools the smoke. Using marijuana bongs allow smoke to be inhaled alot more deeply and rapidly. Results is increased efficiency , thus less marijuana is needed.
Don't use tobacco when smoking a bong. use pure herbs.This way you get pure active elements in your lungs creating a clearer feeling. Tobacco has opposite effect :mixing of tobacco with herbs makes you tired faster. You also need to smoke more to feel good.