Diuretic are essentially any substance that leads to a large amount of fluid to expelled from the body. Diuretics are used today in many places, of which not all are good ways. Lasiks, which is a common medication for patient's with CHF (congestive heart failure) and who suffer edema (fluid buildup), is actually a diuretic, used to expel this fluid, however they are often told get plenty of electrolytes, due to the fact that it also expels minerals and vitamin from the body.
A dangerous use is the use of "water pills", which are pills people take to remove "water weight" (which would work if it weren't for the fact that you can become severely dehydrated and deficient in essential vitamin's and minerals).
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